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Triumph makes a mechanic out of a man

The Bonnie Ref

A Hyperlink Junkie's Illustrated Field Guide
to the 1969 Triumph Bonneville

Bonnie's Maintenance Log

Most recent online update: 4 October 2019

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Classic Triumph/British Forums

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General Shop Info

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Alpha-Numeric Part Number Conversion

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Alpha-Numeric conversion chart



WWW icon Baconsdozen Kevin C. Bacon's history and descriptions of Whitworth (BSW), BSF, BSC, UNC, UNF, SAE, AF, and BA. Includes Bacon's own size charts with conversions to metric and decimal inch dimensions. A must-read, top to bottom, richly informative.
WWW icon "Nuts n' bolts" A thread about nuts and bolts - how can you resist? Some interesting bits on plating, stainless, sizes, threads, and Stuart's run at BSW/BSF wrench sizes.

Common motorcycle threads chart

SAE threads



The British standard threads

Note that while American wrenches are measured across the flats (AF) of the bolt head, wrenches for the bolts in the British standard thread family are measured by the diameter of the bolt's threads.

Chart of wrench size equivalents, Whitworth-BS





Adhesive/Sealant Products


WWW icon John Healy: Where to use Loctite on a Triumph
WWW icon Kadutz: Loctite products in stick format

Speaking of the 'Right Stuff', I think I finally figured out how to get the stuff off! Gasoline and friction.

And speaking of sealing stuff up, should I be using a sealant on the splines for the engine and gearbox sprockets? Too late this year (2018).

Applying Heat

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WWW icon "Heating Engine Cases & Other Parts"

For removal of tight or seized parts, heat is a big help. But for amateurs like myself, The big question is, how MUCH heat? And how to apply it?

Mini Grease Gun

Icon for manual Loading instructions.


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All Lubrication


Manual icon Workshop Manual (1969 650cc Twins) Section A: Lubrication (TOC)
Manual icon Workshop Manual (1969 650cc Twins) Section A2: Routine Maintenance
Manual icon Workshop Manual (1969 650cc Twins) Section A3: Guide to Lubrification Points

Engine Lubrication


Manual icon Workshop Manual (1969 650cc Twins) Section A3: Engine Lubrication
Icon for manual Percentage of Zinc Content for Popular Oils
WWW icon Comments & recommendations (UK & US) on crankcase oil/ZDDP (zinc) and gearbox oil/yellow metals
WWW icon Very informative synthetic oil thread
WWW icon 540ratblog "Motor Oil Engineering Test Data"
WWW icon "Crankcase vent tube discharge question" TR7RVMan elucidates upon Triumph crankcase venting
WWW icon "Tech 101: Zinc in oil and its effects on older engines"

Selecting an Engine Oil

According to the article "Tech 101: Zinc in oil and its effects on older engines", modern oil manufacturers have reduced the amount of 'zinc' (actually ZDDP [zinc dialkyldithiophosphate] or ZDTP [zinc di- thiophosphate]) in their products for various reasons, including prolongation of the life of catalytic converters. When used in older (classic) car and motorcycle engines, the low-zinc products fail to provide sufficient protection against start-up engine wear.

I used a list showing the percentage of zinc content for popular oils to help select an oil with a higher zinc level for Bonnie. I've been using Shell Rotella 15W-40 since around 2014.

Triumph motorcycle lubrification illustration

Changing Engine Oil

The Triumph manual specifies an oil change interval of 1,500 miles. There was no oil filter in the day.

I equipped Bonnie with an oil filter and I change engine oil and oil filter at 1,000 mile intervals. At the same time I change the engine oil, I change the primary chaincase oil, which the manual states should be done at 1,000 mile intervals.


Drain bolts

Note that some Triumph owners/mechanics would council us against removing the crankcase drain bolt because of the risk of contamination. They make the point that it's nearly impossible to clean the area around the drain plug due to its proximity to the case joints and the angle at which the two intersect.

For a long time I cleaned thoroughly around the plug and drained the crankcase with every oil change. Since very little oil drains from Bonnie's crankcase, usually less than a quarter of a cup, I have since joined the camp of cleaning the crankcase drain and oil tank drain once a year. That and other stuff to do after the snow flies.

Using an Oil Filter

At 43,000 miles, I fit Bonnie with a Norton oil filter head, connected as diagrammed below. The mounting bracket was fabricated based on Glenn "Phrog" Davidson's design.

Illustration of Triumph oil line connections for add-on oil filter

Note that the oil tank connections and the oil pipe junction block pipes are 1/4", while those of the Norton filter head are 3/8".

In 2018 I used 5/16" Gates Automatic Transmission Cooler Hose for the hoses connecting to the filter head. The 5/16" is a very tight fit on the 3/8" fittings, and somewhat loose on the 1/4" ones. Ok once clamped - no leaks after several thousand miles.

Filters for use With standard Norton filter head

Filters I used with the Norton filter head satisfactorily include:

Colorado Norton Works Filter Adaptor

Icon for manual Colorado Norton Works Oil Filter Adaptor for Norton Filter Head

In 2017 I picked up a simple thread-in oil filter adaptor from Colorado Norton Works. The adaptor facilitates using filters which are more available and potentially less expensive.

Filters for use with Norton filter head & Colorado Norton Works adaptor

Primary Chaincase Lubrication

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Icon for manual Workshop Manual (1969 650cc Twins) Section A12: Primary Chaincase Lubrication

Draining the Primary Chaincase Oil

The chaincase oil drains slowly because it needs to flow past the primary chain tension adjuster. The drip, drip, drip flow of oil even when it's hot takes hours so I usually give it all day or overnight.

  1. Put wooden blocks beneath the front wheel to tip the chaincase for better drainage.
  2. Remove the drain bolt using an offset 7/16" box end reversed to avoid interference with the frame bolt there.
  3. I use a funnel and a 400ml graduated plastic cup and keep an eye on the amount of oil that drains out.

After replacing the drain bolt, pour 350ml of 30w non-detergent oil into the inspection cap on top of the chaincase.

Caution! Tighten the drain bolt very carefully to avoid stripping threads in the soft aluminum case

Gearbox Lubrication

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Icon for manual Workshop Manual (1969 650cc Twins) Section A11: Gearbox Lubrication
WWW icon "The Effects of EP Additives on Gearboxes"
WWW icon Lucas oil representative 'Don't use our products with yellow metal' (2014)
WWW icon "Bronze-friendly gear oil recommendation?"
WWW icon Comments & recommendations (UK & US) on crankcase oil/ZDDP (zinc) and gearbox oil/yellow metals
WWW icon Hermit's In-progress gearbox oil/yellow metal experiment

Gear Oil Compatibility

There are conflicting opinions about the suitability of different gear oils for gearboxes with bronze thrust washers and bushings. Many, including myself, think GL5 oils are harmful due to their higher levels of sulphur, active and inactive.

On the other hand, many others say there's no problem with the modern GL5 oils. (See the discussion at this link just above)

Some oil companies claim their GL5 products are now safe because they've reduced active sulphur, which eats yellow metals, in favor of inactive sulphur, which is less harmful while still providing the protective coating and added protection of active sulphur. In my book, less harmful is not equal to not harmful.

Gear oils described in the following ways are said not to be yellow metal friendly -

My take is that when a Lucas Oil Products technical director says not to use their products where yellow metals are present (see link just above), I'm inclined to take him at his word.

Where my Bonnie is concerned, no GL5! Finding anything but GL5 or GL5/GL4, though, can actually be problematic if you live in the sticks the way I do. In Spring 2018 I could only find GL5 and GL4/GL5 products within a 40-mile radius, so I had to order a product from online.

From the Red Line description: "Less slippery low sulfur formula compatible with brass synchronizers". "Low sulphur". I'm wondering if there are no sulphur formulations that would still protect Bonnie's precious little gears. The quest continues.

For other gear oil recommendations (including many in UK) see this link above in TriumphRat.

Oil Change Schedule

Draining and Replenishing the Gearbox Oil

There are three hex heads on the bottom of the gearbox: the 3/4" index plunger holder (57-2172); the 7/16BS (3/8W) drain plug with level tube (57-3851); and the 5/16" gearbox level plug (21-0543).

The level plug threads into the drain plug and together they are tucked just inside the frame member on the timing side. Since they are closer to the timing side I always removed and installed them from that side. However, access from that side is awkward due to the proximity of the frame, and recently I realized that it's actually easier to access them from the drive side.

To drain the oil, remove the drain bolt using a 7/16BS (3/8W) socket and a two or three inch extension to clear the frame. Remove carefully to avoid damage to the level tube extending above the drain bolt.

When replenishing the gearbox oil, replace the drain plug after removing the level plug and then add oil, slowly when approaching 500ml, until it overflows from the level plug.

Oil Leaking from Drain Bolts


WWW icon " How to stop oil and gear box drain plug leaks?".

Front fork

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Icon for manual Workshop Manual (1969 650cc Twins) Section A16: Front Fork Lubrication

Draining Fork Oil

WWW icon Gavin Eisler has the following suggestion for draining fork oil::

"When changing fork oil remove RHS top nut, remove LHS drain screw, doing opposites stops oil gushing out the top as the bike settles.Read that in the manual, after doing it wrong for years, this saves a lot of mess. I like to flush the old oil with a little kerosene to get the last of the muck out."

Speedometer Gearbox

Swinging Arm Bushing

The Oil Tank


Icon for manual Workshop Manual (1969 650cc Twins) Section E2: Removing and Replacing the Oil Tank
Parts iconFig.23 Oil tank
Icon for photo Battery Carrier/Oil Tank Mounting (2 photos)
Icon for WWW A thread with some interesting info on oil tanks, oil pumps, and oil flow
WWW icon A thread on repairing Triumph oil tanks
WWW icon Another oil tank repair thread
WWW icon Some ideas on cleaning oil tanks

Removing Oil Tank

  1. Undo hoses
  2. Remove rubber-mounted screw-headed studs and nuts that go through the two top mounting tabs of the oil tank

    Punching them out through the rubber won't work well - use the water pump pliers to pop them out

  3. Battery holder must be removed before oil tank
  4. Remove bottom mounting bracket
  5. Removing oil tank: swing bottom outward allowing the tube sticking out of the froth tower to slide over the top of the frame bracket

Replace Oil Tank

Use Murphy's Oil soap on the rubber parts.

Oil Tank Mounting Adjustment

Important that tank "hangs" well or wear will occur.

One would think that the rubber mounting would incur the wear, but after my first re-assembly there was wear and it was to the tank's mounting peg, not the rubber.

A comfortably loose configuration, adjusted by turning the "C" clamp mounting bracket, should work.

Oil Tank Mounting Measurements

In case you ever need to know, HenryAnthony on forum informs us that the measurement between the barrels holding the rubber upper mounts is 4-1/4", and the measurement between the battery holder straps they bolt up to is 4-1/2".

The Engine

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manual icon Workshop Manual (1969 650cc Twins) Section B: Engine (TOC)
Icon for manual Triumph Overhaul Manual, Unit 650s '63-'67
Parts iconFig.2 Crankcase
Parts iconFig.14 Engine Mounting Plates, Footrests
WWW icon TR7RVMan's advice on preparing for a complete engine teardown
WWW icon Professional Repair Shop (recommendations)
WWW icon "Torque wrench settings", Rod bolt stretch, tappets & cams

Pre-Ignition & Detonation


Video icon  CycleWorld "What Is The Difference Between Normal And Abnormal Combustion In A Motorcycle Engine?" An overview.
WWW icon  Allen W. Cline, CONTACT! Magazine "Engine Basics: Detonation and Pre-Ignition" Detailed explanation.

Above video and article (suggested by Truckedup on both explain pre-ignition and detonation and the difference between them. If I've got it right:

Things to beware of:

Engine Removal and Installation


Icon for manual Workshop Manual (1969 650cc Twins) Section B1: Removing and Replacing the Engine Unit
Photo icon Removing engine using chain hoist
Photo icon Removing engine using floor jack & muscle

Engine Removal

The workshop manual says before removing the engine to remove the two bottom bolts holding the front and rear frames together on the left-hand side. The first time I removed the engine, I removed the forward bolt's nut, which faces out and sticks out a bit, and pushed the bolt in and out of the way. I left the rear bolt that threads into the frame because it didn't seem to stick out much. After the engine was removed from the left side as per the manual, I couldn't see why removing either one was necessary, unless it's to drain water out of the frame: later when I removed the left, rear bolt, about a quarter of a cup of water came out.

The first two times I removed the engine (complete except for the rocker boxes) I used a rope sling to attach the engine to the chain hoist to assist in pulling the engine out of the frame. It worked better the first time than the second, when I raised the engine too high and got it hung upon the bracket on the frame. The ropes have to run on both sides of the frame otherwise the engine will be tilted while being guided into position. This can be seen in these photos:Photo icon Removing engine using rope and chain hoist.

In 2018 I removed/installed the engine (twice!) using a floor jack to support the engine while I lifted it out manually, but only after all the transmission and clutch parts had been removed. Makes a good case for assembling the transmission and gearbox in the frame and not on the bench. Photo icon Removing engine using floor jack & muscle

However the engine is pulled, it's probably better removing/reinstalling the rear/bottom engine mount stud first because the front/top stud has better access for fiddling around. Before inserting the studs through the frame I put a good dab of grease on their ends. Can't hurt.

Reinstalling Engine

T.S. engine mounting plate

D.S. engine mounting plate

Illustrtion of Triumph engine mounting hardware

According to #7 (page 5/ref 38) the bottom bolts on both sides are supposed to have spacers, but they are missing on Bonnie.

Forward engine mount

Bottom engine mount

Head Steadies

Don't be tempted to leave off the head steadies. Apparently they are essential and their absence can result in damage to the frame and/or exhaust ports and exhaust pipes.


I introduced the engine rear end first from the left side. Inserted the front engine mount stud first and then the bottom one. Went up and down a couple of times on the come-along. I drove the stud through from the left-hand side and then used the kickstand as a lever to move the engine to line up the other end.

Oil lines

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Parts iconFig.23 Oil Tank & Oil Lines

Removing Oil Lines

The oil pipes at the oil junction block (70-6930) are 5/16".

The first time I removed the oil lines from the oil junction block I found the job difficult - partly because the outer and inner gearbox covers weren't removed, but mostly because I lacked technique.

After loosening the clamps and sliding them out of the way, try these:

In desperation the first time I used the plastic mallet to rap against the pliers in order to loosen the flexible line. Not a good technique as the WS manual specifically warns against stressing the metal tubes.

Oil Line Connections (stock, with no oil filter)

A Few Important Notes

Improperly installed oil lines can result in catastrophic damage to an engine.

The oil pipe junction block connections described here are for Triumph unit 500/650s. Apparently, connections for pre-unit Triumphs are the exact opposite.

In the following descriptions of oil line connections, 'front'/'forward' and 'rear'/'back' use the front and back of the motorcycle as a reference.

On Bonnie (NC00125) without an oil filter:

Or put another way, 'back to front and front to back.'

Feed Oil Line

Return Oil Line

Oil Line Connections (using Norton filter head)

Bonnie's Norton oil filter head is installed in the return oil line as per the following diagram. Illustration of Triumph oil line connections for add-on oil filter

Crankcase Breather


Parts iconFig.2 Crankcase
Parts iconFig.23 Oil Tank

A 3/8" plastic tube (70-5375 Ref# 39 Fig.2 #7) connects the engine breather pipe stub (70-2724 Ref# 7 Fig.2 #7) just forward of the gearbox sprocket to Tee (70-5370) near the top of the oil tank. Also connected to the tee is the oil tank vent pipe ( 70-6356, Ref# 16 Fig.23 #7), and the oil breather vent tube (82-7353, Ref# 18 Fig.23 #7) which leads to the mayonnaise dispenser at the back of the rear fender.

Oil Breather Vent Tube

The oil breather vent tube passes on the left side just above the indentation in rear fender.

The first clamp is fastened on the left-hand side beneath the left nut holding the strap on top of the fender between the two upper shock mounts.

Oil Pump


Icon for manual Workshop Manual (1969 650cc Twins) Section A7: Stripping and Reassembling the Oil Pump
Parts icon Fig.3 Oil Pump
Photo icon  Oil Pump

Although Triumph made several changes to 650/750 oil pumps, all the pumps are interchangeable (John Healy).

WWW icon Source: thread "Oil Pump Confusion Unit 650cc SOLVED!":

Oil Pressure Relief Valve


Icon for manual Workshop Manual (1969 650cc Twins) Section A6: Stripping and Reassembling the Oil Pressure Release Valve
Parts iconFig.3 Pressure Relief Valve
Photo icon Removing engine using chain hoist
Photo icon Removing engine using floor jack & muscle

Dome nut - 15/16" wrench. Nut behind it - __?__.

Oil Pressure Switch


Parts iconFig.6 Timing Cover
WWW icon TriumphRat forum oil switch thread discussion excerpt.

I have on hand a custom made blanking plug from Walridge for the oil pressure switch that I'm not using on Bonnie. I have never installed it because of concern about whether or not its threads match those in the timing cover. I've read that the casing threads were, at one time, tapered. Putting an untapered plug into a tapered thread hole is said to possibly split the casing. See discussion above.

Cylinder Block & Tappet Blocks

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Icon for manual Workshop Manual (1969 650cc Twins) Section B19: Removing and Replacing the Cylinder Block and Tappets
Parts iconFig.5 Cylinder Block
Parts iconFig.3 Tappet Guide Blocks
WWW icon  J.R. Engineering "Understanding Triumph Tappet Blocks and Pushrod Tubes" Complete rundown of tappet blocks & PRTs on Triumph models from 1945-1982

Replacing Tappet Guide Blocks


Icon for manual Workshop Manual (1969 650cc Twins) Section B21: Renewing the Tappet Guide Blocks
WWW icon Refitting tappet guide block, T140 TR7RVMan nails the drill (pertains also to T120)


On his DVD, Hancox says to line up the hole in the blocks with the locator screw hole in the cylinder block, but doing it this way does not guarantee that the holes for the tappets will be parallel to the camshaft. It is a better idea to make the holes square to the camshaft - the screw holes will be lined up if the block is square to the camshaft.

Due to the closeness of the tappet holes it is difficult to get them lined up perfectly - next time place a straight edge on the edge of the holes and it will be easier to get them properly lined up.

I had to have the guide blocks honed by a machinist before the exhaust tappets would ride up and down freely. Only did this after buying another exhaust guide block, so I have a spare. Illustration of correct orientation of Triumph exhaust tappet guide block

Replacing Tappets

Important: When replacing the tappets in the exhaust tappet guide block, it is essential that the flats on the exhaust tappets face outward as shown at right in order for them to be lubricated properly.

As per above, new guide blocks may need honing to obtain a proper fit for the tappets.

Replacing Cylinder Block

Removing old gasket material is an annoying job. Using a gasket remover product is probably a much better alternative than scraping with razor blades. Loctite makes two such products 1) Loctite 'paint remover', and 2) Loctite 790 'Chiselr Gasket Remover'. Afterwards clean the surfaces with acetone.

Before having a shop hone the cylinders, see these links for John Healy's tips on honing and 'dry' ring assembly. It's about getting a good break-in.


WWW icon "Re: L F Harris Pistons/Rings" (honing cylinders)
WWW icon "Dry ring installation"

After cylinders have been honed, wash them with detergent and hot water to remove all abrasive materials left behind. Dry with clean cloth and apply light coat of oil.

Tightening Cylinder Base Bolts

Can't get on the block nuts with a torque wrench, but using a 6-inch 12-point box wrench (1/2") to tighten them as hard as possible will approximate the proper torque of 35lbs.

Painting Cylinder Block


WWW icon Cylinder paint recommendations?.

Unquestionalably, the best-looking and longest-lasting finish for the cylinder block is powder coat. For tips on other products and surface prep see link above.

Connecting Rods

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Parts iconFig.1 Connecting Rods
Icon for manualTriumph Service Bulletin #317 "Self-locking nuts on big ends" (as shown in #7).



Icon for manual Workshop Manual (1969 650cc Twins) Section B22: Removing and Refitting the Pistions
Parts icon Fig.1 Pistons
Photo icon Removing Pistons
WWW icon "T120 Pistons" (Manufacturers)

Removing Pistons

Triumph pistons packed in ice for grudgeon pin removal

To remove gudgeon pins, heat pistons to around 100C. In 2006 I used way too much heat, so in 2016 I monitored the temperature using the digital laser thermometer. Also in 2016, I first packed snow in plastic bags around the pistons to chill the gudgeon pins before heating the pistons.

In 2016 I was able to push the first pin most of the way out but it wouldn't quite make it all the way. I fashioned a little extractor tool out of a threaded rod, a 3/4" pipe nipple, a short piece of 1/2" copper pipe, and a couple of nuts. (Below, right).

Replacing Pistons

Chill gudgeon pins and, if necessary, heat the pistons. In 2016 I only chilled the gudgeon pins and they slid quite easily through the pistons and the small ends. I thought this was too easy, but the WS-Manual says that's how they should go in. Photo of homemade tool for removing Triumph grudgeon pins

Replacing circlips:

  1. Position one end into the groove in the piston
  2. Place thumb over them
  3. Use angled needle-nose pliers to put in the other end
  4. - Bend as little as possible! -


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Icon for manual Workshop Manual (1969 650cc Twins) Section B23: Removing and Replacing the Piston Rings
Icon for manualTriumph Service Bulletin "Piston Ring Replacement"
Icon for manualTriumph Service Bulletin #323 "Piston Ring Gaps"

Gapping Rings

Installing Rings

Installing rings is pretty straight forward - always from the top and be sure to observe correct order and cylinder for each ring.

Orient the oil scraper rings with their gaps at six o'clock, and the compression ring gaps at three o'clock and nine o'clock.

One advantage of using ring compressors is that the orientation of the ring gaps doesn't change during installation.

Cylinder Head

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Parts iconFig.5 Cylinder Head

I think Bonnie's head has been very lightly skimmed, but I'm not sure. I have no way to measure its height, and anyway, published specs for that vary, as probably did the heads themselves.

Anneal ling and Installing Head Gasket

With only a propane stove or propane torch for heating, I can't heat the entire gasket cherry red to plunge vertically in deep water. Instead, I anneal it section by section. This creates more surface oxidation.

John Healy says that removing surface oxidation left behind by annealing makes for a more professional-looking job. In 2016, the first time I annealed the head gasket, I scrubbed off the oxidation with copper cleaner (lots of work). After the second time I annealed the gasket I let it sit in vinegar overnight. Nearly all the oxidation turned to a brown 'fluff' that rinsed off easily, leaving the gasket 95% bright.

Before installing a head gasket, remove any burring from the head gasket. Burrs, it's said, can become hot spots and cause pre-detonation (pinging).

Apply either grease or Permatex copper to both sides of head gasket before installing. I used the Permatex copper during both head assemblies in 2016. Using a sealing agent will help prevent a) oil leaks, and b) compression leakage between the cylinders.

Oil Leak, 2014/15/16

During 2014/2015 oil was leaking from somewhere on the top end and flowing down the rear of the cylinders, especially the drive side, until it wound up pooling on top of the gearbox.

When I re-assembled after Jan-Mar 2016 top end refresh that leak was gone, but it was replaced by an oil leak from the cylinder base. My last gasket had a bit of a tear on one side, and rather than wait for a new one, I'd used it anyway.

In June (69,575 mi.) I removed the head and cylinders a second time and used Coventry Spares gaskets (from Baxter) for the cylinder head and the rocker boxes (with wire).

Should also note that during first 2016 assembly I used Hypolar on base and rocker box gaskets. I wouldn't do that again. On the second assembly I used grease as I always had. Another option would be a sealant like Loctite 515.

Note: 3,000 miles later and no leaks to date - May 2017 (72,500).

Anti-Seize Compound

For head bolts and spark plugs I think the anti-seize compound is a good idea. However, when it has been used, it's extremely important to thoroughly clean all threads before reassembly.

A method that works well is to first swab out the bolt holes with Q-tips and then fill them with kerosene. Then run bolts in and out, using a rag to mop up the kero and all the crud as they squeeze out. Repeat using brake cleaning fluid.

Installing Cylinder Head & PRTs

See Installing Pushrod Tubes & Cylinder head below.

Torquing Cylinder Head Bolts

Triumph 650 head bolts

Over the years considerable confusion has arisen about correct torque figures for 650 Triumph head-bolts. The confusion is between 15/18 lb (correct) and 18/25 lb (erroneous). According to John Healy, it all eminated from the 1966 Triumph Workshop Manual, whereafter it was possibly printed several times without correction. The figures below are the correct conventional settings.

Torque Figures

Torque figures given are for dry threads. One recommendation is reduce by 20% when wet. So for example, if using anti-seize compound, one would use 15lbs instead of 18. When I've used anti-seize compound I confess I've still used the 18 lb figure.

The head bolts are tightened in the order 1-2-3-4-5-6-7-8-9 as shown in the accompanying illustration, and the final torque rating is reached by incremental steps. For example, tighten all the 18 lb torque bolts to 10 lb, and then 14 lb, and finally 18 lb.

On his DVD, Hughie Hancox starts with bolt #1 and tightens each bolt one by one right to their final torque figure. I tried that method in 2006 and it worked ok, but I feel more comfortable using the incremental 'round robin' method.

The 1/4 inch rocker box bolts and the rocker box stud nuts are torqued to just 5 pounds. Be careful. Install bolts and nuts at least finger tight before torquing head bolts. Doesn't hurt to tighten these fasteners incrementally among themselves and in conjunction with the head bolts. In the end the three nuts can be loosened slightly and re-tightened to obtain an identical torque.

Re-Torquing Head Bolts

After the first heat cycle(s) when the head has been removed and replaced, the head-bolts must be re-torqued to compensate for their looseness due to the "bedding-in" of the cylinder gasket, cylinder head, and bolts.

Because torque figures pertain to bolts when they are turning, it's not effective to just start tightening them. That would most likely result in over-torquing, which is never a good thing. So, the method is:

Note that the bolts don't actually loosen themselves, they loosen relatively, due to compression of the head gasket and stretch of the headbolts. Nevertheless, the question arises in many minds, were the bolts actually "loose" before re-torquing, and if so by how much? One way to find out is to mark one point of each headbolt and then make a corresponding mark on the head. After you re-torque you'll see whether it was necessary to re-tighten each bolt.

And as the "Duke of Oil" pointed out on, given their thread factor and how far the bolts turned to get back to spec it's possible to calculate how much the head gasket compressed and the head bolts stretched.

Cleaning Cylinder Head

If you're ever tempted to try cleaning up a Triumph cylinder head with oven cleaner, think twice lest the head winds up looking Photo icon this way. It took bead-blasting to remove the resulting corrosion.

There's no substitute for rags and q-tips and kerosene and brake cleaner and elbow grease.

Rocker Boxes

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Parts icon Fig.5 Rocker Boxes

(See page B2 in workshop manual)

Replacing Rocker Arm Spindles

As per WS and Hanyes manuals, I used a 5/16" bolt ground to a taper at one end to help line up the flat and spring washers before inserting the spindles. With enough fiddling around they eventually go on.

If a spindle doesn't go quite all the way in it is probably due to the last set of washers (flat and spring) hanging up on the shoulder at that end. Move them around and tap lightly on the end of the spindle with plastic mallet. When everything is lined up it takes only a very light tap.

Thackary Spring Washers


Manual icon Triumph Service Bulletin #25 "Lubrication - Rocker End, Ball Arm"
WWW icon November 2013 thread and November 2010 thread and March 2017 thread.

Because the Thackary spring washers could become fouled in the rocker arm notches and therefore block oil flow, Triumph reversed the position of the Thackary spring washers and the flat thrust washers .

Putting the Thackarys against the rocker box cases instead of the rockers is supposed to allow for a greater oil flow. However, the swap should only be made when using rocker shafts that have a lengthwise groove (my Bonnie's don't).

When placing the Thackary washers against the rocker box (the updated parts order) as opposed to against the rockers (the original order), the 3/8" flat washer has to be replaced by a 1/2" flat washer so it will clear the shoulder on the rocker shaft.

I tried the new assembly order once or twice and had trouble fitting the spindles so I went back to the #7 layout, as illustrated here. This ends well because Bonnie's shafts are not grooved.

Starting from TS, the original #7 layout as used by Bonnie:

The updated layout (NOT used by Bonnie):

Rocker Arm Spindle O-Rings


WWW icon Ed Holin "What is the correct O ring for the rocker spindles on a '71 Triumph T100R and similar bikes?".
WWW icon TriumphRat Tips on installing and sealing the spindle o-rings.

When replacing the rocker shaft o-rings (ref#29 Fig.5 #7), don't use the 70-3253 listed in #7. Use updated, better fitting part 60-3548. And be sure it's Viton.

For what it's worth - Tool icon special tool Z111, rocker spindle oil seal compressor, is available. I've never found it effective or helpful.

Removing Rocker Boxes

Not strictly necessary to remove the ignition coils, but man, do they ever shine with metal polish and elbow grease! After removing gas tank, torque stays, and the domed nuts and copper washers from the oil lines, gradually release the torque from and remove:


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Pushrod Tubes (PRTs)


Parts iconFig.5 Pushrod Tubes
WWW icon  J.R. Engineering "Understanding Triumph Tappet Blocks and Pushrod Tubes" Complete rundown of tappet blocks & PRTs on Triumph models from 1945-1982

Pushrod Tube Styles

Two different pushrod tube designs were used between 1968 and 1973 on "B" range 650 machines:

Bonnie, a 1969 model year built in Oct 1968, has the one-piece design.

Pushrod Tube O-Rings


Manual iconTriumph Service Bulletin #18-69 "PRT o-rings leaking oil - 1969 'B' & 'C' Range"

Oil leaks from the pushrod tubes are a perennial problem for many Triumph owners. In 1971, Triumph specified a red, high-temperature o-ring (E111283) for use on top. They were supposed to resist the higher temperature between the exhaust PRT and the cylinder head. I tried the red o-rings twice and found that they crumbled pretty quickly both times.

Later, the 71-1283 o-ring became available in Viton, and Viton is the only way to go. On Bonnie I use 71-1283 o-rings in Viton top and bottom and they have never leaked appreciably. (Knock on wood).

The following table details the different PRT o-rings used between 1969 and 1971.

  #7 ('69) '70 USA '71 USA
Bottom o-ring 70-7310 70-7310 7310
Top o-ring 70-7310 70-7310 71-1283
Sealing ring 70-4752

Pushrod Tube Seals


Manual iconTriumph Service Bulletin 324 Pushrod tube oil seals

Pushrod tube oil seals were a modification introduced by Triumph around 1971. These oil seals are at the bottoms of the PRTs, between the PRTs and the tappet guide blocks.

For a better seal, the upgrade uses a square-sectioned sealing ring retained by a metal band (the "wedding band") at the base of intake and exhaust PRTs.

The square-sectioned sealing rings are commonly, but not always, white silicon. I've had black, sponge-like seals and they worked fine. These seals come in different thicknesses to enable adjustment of "the crush". (See section below).

Bonnie's been upgraded to the parts shown in Figure 4 of the Triumph '71 USA parts book.

Pushrod Tubes and "Crush"


WWW icon John Healy, Vintage Bike Magazine "Push Rod Tubes"
WWW icon thread Discussion of PRT 'crush'
WWW icon thread Discussion of PRT sealing rubber protruding
Video icon YouTube Raber's Tech Tips, Episode #3 - Triumph 1967 T120 Bonneville Pushrod Tube Seals

Note: this section updated 5 June 2019 to reflect the proper usage of the term 'crush'.

'Crush' refers to the amount of compression of the seals and o-rings at the bottoms and tops of the PRTs respectively when the head bolts are tightened down. Too little crush means the seals are compressed insufficiently to create a good seal, resulting in oil leaks. Too much crush results in the seals holding the cylinders and the head apart and further tightening of the head bolts can cause the alloy head to warp.

When the head is sitting freely (loose bolts) on top of the cylinders with the head gasket and PRT seals and o-rings in place, there should be between .030" and .040" gap between the cylinder head and the head gasket.

If the gap is too wide there will be insufficient crush, resulting in a poor seal and oil leaks. If the gap is too narrow there will be too much crush, risking distortion of the head when head bolts are torqued down.

The gap, and therefore the crush, are adjusted by substituting different thicknesses of sealing rings. A thicker sealing ring holds the PRTs and the head higher, increasing the gap and reducing crush. A thinner seal makes the gap smaller, increasing the crush.

For dimensions of sealing rings & o-rings see table below.

Install head with bolts 6,7,8,and 9 fitted evenly and lightly enough that the bottom seals and top o-rings are not being compressed. Then check for a suitable gap that is even all the way around.

Installing Pushrod Tubes & Cylinder Head

Although one of Bonnie's pushrod tubes seats very tightly at the bottom and the other is relatively loose, they both seem to seal well to the tappet block once the head is bolted down and the sealing ring squashes out to the wedding ring.

Be sure to oil the top and bottom o-rings before assembly (sharp edges ahead). It's also ok and good to grease the top o-rings to help hold in place as well as lubricate.

In 2016, I used 'Right Stuff' on the top o-rings during first assembly. Upon disassembly 450 miles later, I picked the Right Stuff 'slime' out of the o-ring groove. No more 'Right Stuff' for me. Back to oil and grease.

When installing the head, it may go better to maneuver it into place from the rear, as opposed to from one side or the other.

Slight in & out adjustments (punch and ball peen) to the tabs at the top of the PRTs can sometimes ease installation or removal of the PRTs. Just be sure the tabs don't foul the pushrods when they are installed.

PRT O-Ring & Seal Dimensions

When adjusting for proper sealing ring crush, the following dimensions could be helpful.

Component Height
Cylinder Head 2.755"
2.785 (Internet forum)
Head Gaskets .045-.050
Round o-rings 70-7310 (Buna-n) / 71-1283 (Viton)
ID=.987"/Nom 1" CS=.103"/Nom 3/32" OD=1.193"/Nom 1 3/16" Dash#120
Square-sectioned sealing rings 71-1190 Thick= .033" (Raber's)
70-3547 Thick= .093"/nominal 3/32" (.091 Raber's)
70-4752 Thick= .125"/nominal 1/8") (.123 Raber's)
70-1496 Thick=.1875"/nominal 3/16" (.177 Raber's)
Pushrod Tubes 70-9349/71-2575

Source: unless otherwise noted, dimensions are from John Healy's article 'Push Rod Tubes' in Vintage Bike Magazine.

Rocker Box Gaskets


WWW icon "Gasket sealer for top end "

I've used wire-reinforced (BCS and Walridge), plain paper (MAPCycle), and paper & metal sandwich Covseals (Baxter) for rocker boxes. Covseals made the best seal, followed by MAPCycle's plain paper. Wire-reinforced gaskets were my least favorite.

I used the Covseals dry as per included instructions. I have noticed some very slight weeping and after reading the post just above I think I will apply a little sealer to them the next time. There's also some very good advice about sealing PRTs in the same post.

Replacing Push Rods and Rocker Boxes

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Icon for manual Workshop Manual (1969 650cc Twins) Section B2: Removing and Replacing the Rocker Boxes

I label the push rods with a marker when I remove them & replace in their same position. If I remember, else not. As I replace the push rods I examine them and, ideally, make note of anything special, such as wear to the cups.

  1. With a good dab of grease filling the bottom pushrod cups, lower the pushrods down the pushrod tubes until you feel them contact their respective tappet. When properly seated, the tappets 'stick' in the greased pushrod cups and you can feel the tappets being pulled and pushed up and down by the pushrod.
  2. Without lifting the pushrods off their tappts, fit the rocker box gasket holes over the pushrods, line up all the gasket bolt holes, and press the greased gasket flat.
  3. Last year I used the Covseals 'dry'. Removal this winter was arduous. This year I greased both sides, let them sit an hour, and wiped off excess before putting them on with a couple extra small grease dabs to hold things in place while installing the rocker box.
  4. Double-check the pushrods for engagement with the tappets and have the pushrods standing straight, and parallel with each other.
  5. Before installing the rocker boxes, give a few squirts of oil to moving parts.
  6. Introduce the rocker box from the middle, and, looking up from below, manoeuvre it into place without touching the pushrods. When the three studs are lined up on their holes, gently let the rocker box down onto them.
  7. Fit the two large engine bolts first. They won't quite clear the frame so put the washer on the hole and then insert the bolt through it until the nut just touches the frame on one of its flats. With both hands on the rocker box, gently rock it side to side, barely lifting it, and the bolt will drop down past the frame with a snappy retort.
  8. Finger-tighten the head bolts loosely, and then put the three nuts/washers on the studs before finger-tightening the small rocker box bolts.
  9. I go back and forth between the head bolts (70-1596, BS 3/8-26TPI X 5 7/8 U.H. Tool-3/8BS-5/16W Torque: 18 LBS), rocker box bolts (21-1875, UNC 1/4-20TPI X 2 5/32 U.H. Tool-3/16W Torque: 5 LBS), and rocker box stud nuts (82-0879 BS 1/4-26TPI Torque 5 LBS). I tighten gently, then loosen, then tighten a little more then loosen a little, etc, until all the nuts and bolts are snug and evenly tightened.

Lightweight Pushrods & Rocker Box Gasket Modification

When I tried using lightweight pushrods it was necessary to modify the rocker box gaskets to accommodate their larger diameter. After modification the gaskets no longer served to guide the pushrods to the rockers when fitting the rocker boxes, so I made a template to guide the pushrods, split it in two, taped it back together for assembly, and removed in two pieces when the rods were placed.

Photo of Triumph pushrod installation

Replacing Engine Torque Stays


Parts iconFig.14 Engine Torque Stays
Photo icon Engine Torque Stay Fasteners.
WWW icon StuartMac on assembling the engine torque stays


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Parts iconFig.5 Valves
WWW icon Vintage Bike Magazine John Healy: "Where is your valve seat?"
WWW icon "Oversized valves fix deep seats?" A very educational thread!
Video icon YouTube  Lunmad: Valve Clearance Adjustment

Note that in the video above, Lunmad uses a slightly unorthodox method to open valves for adjustment.

For example, instead of, as per the WS Manual, opening the DS exhaust valve (pushrod up, rocker down) to adjust the TS exhaust valve clearance, Lunmad closes the TS intake valve.

Tip When checking or adjusting valves with the gas tank on the bike, Lunmad's method makes it much easier to adjust the TS exhaust valve.

Replacing Valves in Head

Illustration of Triumph valves, valve springs, and collets

Install valves, springs, and retainers as per figure at right. Use red valve spring compressor and grease the split collets to help hold the first in place while inserting the second one.

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Adjusting Valve/Rocker Clearance


Icon for manual Workshop Manual (1969 650cc Twins) Section B5: Adjusting the Valve Rocker Clearances

When adjusting the valve rocker clearances, it's better to have a tiny bit too much clearance between the valve stems and rockers than not quite enough. Too little clearance and the valves may not fully close once the engine is hot. On the other hand, too much clearance means the rockers will 'hammer' the valve stem tips.

Note that after the rocker boxes, head, and/or cylinders have been removed and replaced, or any time the head bolts have been re-torqued, it's important to re-check the valve rocker clearances after a brief run-in. All the conditions above will compress the gaskets and therefore decrease the clearance between valves and rockers. Symptoms of this include excessively high engine temperature, loss of engine power, and low compression due to the exhaust valves remaining slightly open.

Sound can be a useful guide to setting valve rocker clearance (see 'Adjustment by sound and feel', just below), as well as when evaluating correctness of settings with the engine running.

It's much easier to adjust valve clearance while the carburettors are removed, but adjustment can also be done with just the gas tank and air filters off.

If you got carried away tightening the valve inspection caps and are having trouble getting them off, gently heating the rocker box cover around them will loosen them right up.

Valve adjustment tools

The stock Trimph adjustment pins have square heads which make adjustment quite vague. If you're using the square-headed adjustment pins you may want to check out the two-piece valve adjuster tools that are available. In theory these should make adjustment a snap because they allow you to control adjustment with thumb and finger while simultaneously tightening or loosening the locking nut. In practice, the fit between the adjustor and the square pin is too sloppy to give good control.

I find the readily available adjustment pins with hex heads are a big improvement as they make it easier and more accurate to gauge the degree of change in adjustment. With these pins you get good control with an allen head wrench handle as you tighten or loosen the adjuster pin locknut with a short 7/16" box-end wrench.

Coarse adjustment by position

Valve clearances should be set to .004" for exhaust and .002" for the intakes. A common method of obtaining 'ballpark' settings is to run the adjustors in until they just contact the valve stems by feel, and then back them off 1/8 of a turn for exhaust, and 1/16 turn for intake.

Adjustment by sound and feel

Another common adjustment method is to grasp the rockers with thumb and index finger and rock them up and down:

Positioning Valves for Clearance Adjustment

In order to adjust a valve's clearance, the valve must be closed. To position a valve in its closed position (rocker up), make the opposite valve fully open (rocker down).


Formally, I had difficulty getting consistent valve clearance measurements, probably due to inaccurate positioning of the valves. I've improved this in two ways: using the rear wheel instead of the kickstart lever to do the fine positioning, and by using a finger to gauge when a rocker has reached to lower limit of its travel.

So, to adjust the DS exhaust valve, make it closed by opening the TS exhaust valve as follows:

  1. Place fingertip on TOP of the adjuster screw of the TS exhaust valve rocker

    Do NOT place finger anywhere but on TOP of the rocker.
    Getting a finger caught between the rocker and the rocker
    box would be like sticking your finger in a guillotine!

  2. Put the bike in second gear and rotate the rear wheel forward, making the TS rocker move downwards
  3. Continue rotating the rear wheel forward until the TS rocker just begins to rise again
  4. Now rock the rear wheel back and forth until the TS rocker is positioned all the way down
  5. The TS valve is now open and the DS valve is fully closed and ready for adjustment

On adjusting the clearances:

Adjustment after Re-torqueing

When head has been removed and replaced, valve clearance needs to be re-adjusted several times due to gasket 'crush'.

  1. After running the engine stationary for several minutes in shop
  2. Again after a short ride of several miles
  3. Again after re-torqueing the head bolts

Engine Compression

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Video icon YouTube Lunmad: Compression Test

Compression Test

Testing engine compression is a quick and easy way to determine an engine's general health with regards to valves, rings, and cylinders.

Five easy steps:

If compression is low, add small amount of oil to the cylinders and retest.

If valves are suspected, check to ensure there is adequate valve clearance to prevent valves from closing fully.

Sudden Loss of Compression


WWW icon "1969 T120R magically loses compression"

A sudden loss of engine compression can result from gas washing the pistons. In August of 2018, after sitting for ten days, the Bonnie seemed to give up all compression after the first kick. TR7RVMan on correctly diagnosed the problem and offered a solution which consisted of pouring a couple of tablespoons of oil down the plug holes, kicking over the engine several times with the plugs out to remove excess oil, replacing the plugs, and starting as usual. The method worked perfectly and normal compression was restored as soon as the bike started. And no problem during the following days.

Bonnie's Compression Check History

Year / Mileage Cylinder Opp Plug In Opp Plug Out
2016/68,500mi - 3 heat cycles after top-end job Left   120
Right   120
    Opp Plug In With Oil
2015/68,500mi Left (250F) 60 90
  Right (205F) 90 80
    Opp Plug In Opp Plug Out
2014/60,500mi Left - 135
  Right - 145-50
2010/43,500mi Left 145 150
  Right 120 150
2006/Frank's - After break-in Left 165-170 -
  Right 165-170 -
2006/28,600mi - Right after top-end rebuild Left 135 -
  Right 135 -

Timing Chest

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Parts iconFig.6 Timing Cover
WWW icon "Removing timing cover"

Cam Timing


WWW icon "How to Degree In Your Camshaft" (PDF)

Ignition Timing

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Video icon Lunmad: Ignition Timing

Note that the timing mark on Lunmad's 650 rotor corresponds to TDC. On Bonnie the timing mark corresponds to 38 degrees BTDC. As mentioned by Lunmad in the comments section, use the flywheel locator tool to determine which location the timing mark on your bike's rotor represents.

Setting Ignition Timing with Points


WWW icon Hermit's Illustrated Ignition Timing with Points Complete instructions for static and dynamic timing using points.
WWW icon TR7RVMan: Ignition Timing w. Points Don details many finer points about setting up points... Definitely a must read!
WWW icon "Anyone still running points ignition?" Lots of love for points here, but only a couple of good pointers.

The contact breaker points gap for late-60s 650 Triumphs is .014-.015-.016". Follow links just above to "Hermit's Illustrated Ignition Timing with Points" and TR&RVMan's superb post on points ignition timing for just about everything you'll ever need to know about the care and feeding of ignition timing with points.

Setting Ignition Timing with Pazon


Photo showing Pazon electronic ignition installation Manual icon Pazon installation, timing, and trouble-shooting

Static Timing

Use a flywheel locator tool (OR timing pointer and rotor timing mark if the one on your rotor points to 38 degrees BTDC and not TDC) to locate 38 deg advance.

Dynamic Timing

Use strobe on either cylinder for dynamic timing Illustration of timing marks on Triumph rotor

It would probably be helpful to establish corresponding reference marks on the Pazon disk and the timing cover.

Replacing rotor cover after timing

If the cover is installed on the chaincase before screws are inserted, mating the first screw to the threads in chaincase can be annoying. Easier to find the hole by inserting the top screw in the cover and fitting both together dangling from a Phillips screwdriver.

Removing magnetic rotor center

Use Metric M8 bolt threaded into rotor.

Spark Plugs


Manual iconTriumph Service Bulletin #12-68 "Spark Plug Cross Reference Chart"
WWW icon NGK-spark Trouble-shooting Dry & Wet Fouling of Spark Plugs
WWW icon How to Read Your Spark Plugs

Used NGK for quite a while, but have returned to using Champion N3C (new Champion designation 801).

Plug gap: .025". Chart showing NGK sparkplug heat ranges

Interpreting NGK plug designations:
B= 14mm plug thread
7 = Temperature range
E = 19mm plug thread reach
S = Standard super copper core electrode

The higher the NGK number, the colder the plug
The lower the Champion number, the colder the plug

Exhaust Pipes and Mufflers

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Icon for manual Workshop Manual (1969 650cc Twins) Section B13: Removing and Replacing the Exhaust System
Parts iconFig.15 Exhaust System

I have Bonnie's original headers with crossover pipe in inventory, but I replaced them with non-crossover types on the bike.

When removing the exhaust header pipes and mufflers, remove them as a unit on each side. Simply remove or loosen the exhaust pipe clamps, the exhaust pipe engine bracket Phillips heads screws, and the muffler hanger bracket bolts.

When removing or replacing the exhaust pipes over the exhaust pipe adaptors (spigots), it's ok to hit them with a plastic mallet as long as you place a thick, folded rag over the pipes and don't go crazy.

The Transmission

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Icon for manual Workshop Manual (1969 650cc Twins) Section C: Transmission (TOC)
Parts iconClutch, figure and part listing
Parts iconPrimary Chaincase, figure and part listing
Video icon YouTube Raber's Tech Tips, Episode #4 - Triumph Unit Construction Twins Cush Rubber Installation
WWW icon 'Unit 650 clutch thrust washer' Clutch thrust washer discussion, inc. types & changes in size.
WWW icon TR7RVman's clutch tips Restoring & maintaining the Triumph clutch.

Primary Chaincase

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The primary chaincase houses the transmission, which consists of the engine sprocket, the primary chain, and the clutch assembly. The transmission's job is to transfer energy from the engine sprocket to the gearbox mainshaft, the gear cluster, and subsequently to the gearbox sprocket and rear wheel.

Primary Chaincase Lubrication

See Lubrication Schedule, Primary Chaincase

Primary Chaincase Cover and Gasket

WWW icon 'Primary Case removal'

If your primary chaincase cover is good and flat, try this tip: put gasket sealer on the side of the gasket that goes to the cover and grease the side that goes to the chaincase. Chances are that the next time you remove the cover the gasket will stay on the cover and you can re-use it upon re-assembly.

If you're having difficulty removing the chaincase cover, or keeping the gasket in place while putting it back on, have a look at this thread on

Adjusting Primary Chain Tension


www icon Side-by-Side photos illustrating Primary Chain Wear When adjusting 'slipper' becomes too arched replace the chain.

www icon Primary Chain adjuster This thread relates to a T140, but includes a lot of info that also pertains to the 650s as well.

In order to adjust the primary chain tension, the oil must be drained from the primary chaincase, so it's only logical to check the tension at each oil change and adjust if necessary.

  1. Drain the primary chaincase oil..
  2. When oil has finished draining, insert Tool iconPrimary chain tension adjuster D2108 into the drain hole.
  3. Hold engine against compression with kickstart lever (Manual iconService bulletin 1-69, January 27, 1969)
  4. Use a screwdriver to turn the adjustor tool in to tighten, out to loosen
  5. Through the inspection cap on top of the chaincase, move chain up and down with finger or wire and adjust total up and down free play for (3/8") (1/2").

Note that excess tightness could wreak havoc with crankshaft bearing and/or clutch and/or mainshaft. Too loose and you'll begin hearing strange noises from the primary chaincase, with possibility of damage to stator or casing.

Dismantling the Transmission

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The clutch assembly, engine sprocket, and primary chain are removed simultaneously as one after slacking the chain and removing the stator and rotor.

Exploded figures with parts numbers and specs:


  1. Drain chaincase oil and slacken primary chain Tool icon Primary chain tension adjuster D2108
  2. Slack off the left side foot peg (3/4" box end) and rear brake adjustor
  3. Remove cover screws using your Posidrive screwdriver and a 1/2 wrench for the domed stator stud nuts 21-0544 (3)
  4. Remove chaincase cover
  5. Remove 70-4565 rotor nut with 9/16BS wrench or socket
  6. Remove 14-0702 locking nuts (3) from stator studs (13mm deep socket is a perfect fit)
  7. Free alternator wires and remove stator
  8. Remove Rotor Tool icon Wheel Puller
  9. (Store rotor AWAY from metal/magnets)
  10. Loosen engine sprocket (Tool icon Engine Sprocket Puller)
  11. (Remove 14-0403 locking nut (9/16) and adjusting pin from pressure plate)
  12. Remove 57-2526 clutch pressure plate adjustment nuts (3) using Tool icon clutch pressure plate spring adjustment tool
    Bit of a PITA due to 'pips' under heads - WS Manual says 'Put a knife under head of nut to facilitate removal' - never works for me until they're already part way out
  13. Remove Pressure Plate
  14. Using a hook for friction plates and a magnet for steel plates, remove clutch plates and carefully stack in same order they were installed.
  15. Remove 21-0586 (self-locking) clutch nut using Tool icon clutch locking tool & a 7/8 socket and breaker bar.
    If difficult to remove, use air wrench
  16. Loosen clutch center from mainshaft (Tool icon Clutch center extractor) See notes below on removing clutch center xxximage
  17. Remove clutch center, chainwheel, primary chain, and engine sprocket all together
  18. Remove half-moon key from mainshaft

    Have difficulty removing the key from the mainshaft? Here's a tip from TR7RVMan on WWW icon Use end cutter pliers

Notes on Dismantling the Transmission


Rotor nut torque was about right, rotor pulled right off by hand. Once again, the 'self-locking' clutch nut not very tight. Will put the blue to it this time. Kickstart ratchet nut was good and tight, not excessively. Engine sprocket, clutch wheel/center all popped off easily with their respective tools.


Things looked pretty good this January when I tore apart the transmission and gearbox. The primary chaincase and clutch assembly were still quite clean. There was some gray (metal) in the gearbox.

Possibly some wear evident:

Things that were kind of loose:

Notes on Removing the Clutch Center


In 2016 I began carefully tightening down the extractor tool and just as I was getting ready to stop and give it a whack with the brass hammer, the center popped off the () mainshaft. Not surprising as the taper on that shaft was very pitted.


The extractor tool only engages the clutch center threads by about a half-inch and in 2015 I stripped its threads.

When the replacement tool from MAPCycle arrived, I applied WD-40 to the clutch center and 'pre-stressed' it with the new extractor for a couple of days.

When it still wouldn't release, I tapped against the inside of the clutch center with an aluminum drift. Then I tried striking the "loaded" extractor tool with a brass hammer. Still nothing moved.

Finally, after researching BritBike Forum, I tried the air wrench. After about 20-30 seconds of gentle hammering at the wrench's lowest setting, the center released from the mainshaft.

That's when I saw that the main shaft/clutch hub key had Photo icon sheared off length-wise. I also noted that the clutch hub had spun on the mainshaft.

Clutch Center & Thrust Washer Compatibility

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WWW icon John Healy: Thrust washer/clutch center compatibility
WWW icon 'Unit 650 clutch thrust washer' Thrust washers, discussion of types & changes to size
Photo icon Early and late clutch centers/thrust washers

The original clutch center (57-1734) uses the 57-1735 thrust washer. Bonnie was upgraded in 2015 (65,000 miles) to use an upgraded thrust washer (57-3931) and clutch center (57-3929).

These parts are not mix-and-match as the inner diameter of the thrust washers are different.

Both thrust washers (57-1735 and 57-3931) are, or were, available in different materials:


The spec given for thrust washer thickness is .052/.054".

Reassembling the Transmission

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Reassemble the Clutch Center

  1. Lay the clutch center flat
  2. Slather it with grease
  3. Position the 20 rollers
  4. Put on the thrust washer, copper/brass side up (out, to clutch plates)
  5. Place the duplex sprocket over the clutch center
  6. Put on the clutch hub assembly (shock absorbers, plates, spider) inside the sprocket
  7. Give a few taps with plastic mallet to seat everything

Reinstalling Engine Sprocket & Clutch Assembly

See Sprocket Alignment note just below.

  1. Install moon-shaped key to mainshaft, well-greased
  2. Position mainshaft with the key at 12 o'clock
  3. Place chain over engine sprocket (long shoulder to oil seal and bearing) and duplex sprocket
  4. Arrange the sprockets so the keyway in the clutch center is at 12 o'clock
  5. Offer the sprockets to the crank and main shafts
  6. It's possible/helpful to tip slightly forward the duplex sprocket and peer down to align the keyway with the key
  7. Tap with plastic mallet if necessary
  8. Install self-locking clutch nut and thick washer to end of mainshaft with blue Loctite
  9. Use deep-well socket and plastic mallet to seat the engine sprocket
  10. Torque clutch nut to 50lbs - it is recommended to use Loctite on the clutch nut
  11. DO NOT install clutch plates & pressure plate yet
    You'll need to use the clutch locking tool in order to accurately torque the rotor nut to 30lbs
    See torqueing the rotor nut just below
  12. Install distance piece over crankshaft, chamfer towards sprocket
  13. Install 71-0082 woodruff key and rotor
  14. Install 70-3975 tab washer and 70-3977 shouldered rotor nut
    Exploded view of Triumph main bearing, engine sprocket, and rotor in primary chain case
  1. Apply blue Loctite and tighten the rotor nut to 30Lbs
    When torqueing the rotor nut, be sure to use clutch locking plates to hold the crankshaft and not 4th gear and brake.
    When using 4th gear and the rear brake, part of the applied torque is absorbed by the clutch shock absorber rubbers, resulting in improper rotor nut torque (John Healy,
  2. Now install clutch plates and pressure plate and adjust for true

Additional Notes

Adjusting the Pressure Plate

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WWW iconTriumphrat Forum Peg's clutch plate adjustment method

The pressure plate should be adjusted so that it applies pressure evenly to the clutch plates and also so that it lifts evenly. Using a Tool con clutch pressure plate spring adjustment tool, adjust the three pressure plate spring adjustment nuts until the pressure plate is 'wobble-free' as it turns while depressing the kickstarter with the clutch handle held in. Also check to see that the pressure plate is lifting evenly all the way around as the clutch handle is pulled in.

Hope to make a standard with a pointer to assist in this operation the next time.

Pretty sure I over-tightened the clutch adjustment screws in 2014 and probably under-tightened them in 2015 (slipping?).

Adjusting the Clutch Operating Mechanism & Cable

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Video icon YouTube Raber's Tech Tips, Episode #1 - Triumph Unit Twin Clutch Pushrod Adjustment

As shown in Rabers' video just above:

  1. Loosen the clutch cable adjustment at the handlebars until the cable is slack
  2. Remove the inspection plug in the center of the primary chaincase cover
  3. Inside the inspection port, slack off the locking nut on the clutch rod adjuster screw
  4. Make sure the lock nut is backed well off
  5. Using a screwdriver, slack the adjuster screw and then tighten it until you find the exact spot that the pressure plate just begins to lift
  6. When the pressure plate is just at the point of lifting, double-check to make sure the cable is still slack
  7. Back off the adjuster screw...
  8. When the adjuster screw is backed off, tighten the lock nut
  9. Complete the operation by adjusting for 1/8" play in the clutch cable at the handlebars

Clutch Rod Mechanism Pops or Clicks

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If the 3-ball clutch rod operation mechanism develops a popping or clicking noise when pulling in the clutch lever it means the mechanism is out of its adjustment range. To correct the problem, follow the procedure just above to adjust the clutch operating mechanism.

The Gearbox

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Icon for manual Workshop Manual (1969 650cc Twins) Section D: Gearbox (TOC)
Parts icon Fig.9 Gearbox outer cover  /  Fig.7 Gearbox inner cover  /  Fig.8 Gearbox, gears and shafts
WWW icon Index to all 8 of Hermit's Illustrated Gearbox Articles
Tool icon Triumph Service Bulletin #329 "Third gear ratio and selector forks modifications"
WWW icon Links John Healy on 4 and 5-speed Triumph gearboxes including leaf-springs versus plungers
WWW icon Kevin Roberts' "Upgrading a 5-speed gearbox" Includes excellent photos and informed discussion of Triumph gearboxes.

Hermit's Gearbox Illustrations: Stills & Animations

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Photo icon Stills, Rear View
Video icon Gear Animation, Rear View (wait for it)
Photo icon Stills, Front View
Photo icon Gearshift lever & gear shift quadrant deflection from center
Video icon Gear Animation, Front View (wait for it)

Gearbox Lubrication

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See Lubrication Schedule

Gear shifter lever

2003, 2006

Twice I failed to tighten the gear shift lever bolt sufficiently and lost the gear shifter. In 2003 the lever fell off about a week after being back on the road. I heard it hit the road and went back for it. In 2006 if fell off about 75 miles into the new season. When I realized it was gone I backtracked and found it on the shoulder two miles back.

Gearbox Problems

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Manual icon Triumph Service Bulletin #329 "Third gear ratio and selector forks modifications"
Manual icon Triumph Service Bulletin #8-59 "1969 650s jumping out of 2nd/3rd gears"
Manual icon Triumph Service Bulletin Trouble-shooting excerpt: "Improper Upshift, Third Gear"
WWW icon "Gear selection malfunctions after gearbox overhaul" The thread I started on Bonnie's shifting problem
WWW icon "69 Bonneville jumping out of gear"
WWW icon "T120 unit gearbox problem"
WWW icon "Gear Lever movement" Faulty gear selection thread
WWW icon "Gear shifter hangs up when down shifting" Don packs a lot of good advice about diagnosing gearbox problems into this post
WWW icon John Healy: 4/5-speed gearbox conversion Inc. photos comparing 4- & 5-speed components
Video icon YouTube Lunmad: Gearbox Video

Jumping out of Gear

The problem of jumping out of 1st gear plagued Bonnie for over two years. Eventually I came to view the problem as being with down-shifting more than popping out of gear. That's when I began to suspect the gear change quadrant.

When I finally replaced the gear change quadrant in June of 2016, it fixed the problem straight away. The old gear change quadrant hadn't traveled far enough when down-shifting, leaving 1st (and sometimes 2nd and 3rd) gears selected incompletely. The downshift travel of the new unit from Baxter traveled about 3/32" further than the original.

With the new gear change quadrant installed in the outer cover, I fitted a degree wheel to it to observe how far the gear change quadrant deflected from center when the gearshift lever was moved to the up and down-shifting positions. The up and down-shift deflections were nearly identical: 19 degrees for upshift, and 19-1/2 degrees for downshift.

Outer Gearbox Cover

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Parts iconFig.9 Gearbox outer cover

Some say an outer gearbox cover gasket can cure certain gearbox problems, but it did nothing for Bonnie. Since fixing Bonnie's gearbox I've used no gasket because she didn't come with one and it's not necessary for sealing - Hylomar or other sealant will take care of that.

Kickstart Lever Tapered Pin


WWW icon "Stuck kickstart pin"

Removing the tapered pin holding the kickstart lever in place is not always so easy. The pin gets bent out of shape by the force of repeated kickstarts, effectively jamming itself in the bore. It sometimes helps to jam the kickstart lever forward using a plastic mallet and then whack the pin smartly against the nut threaded flush.

As noted in the thread above, some kickstart pins are made of harder material than others and they tend to distort less than softer ones.

When replacing the tapered pin, be sure to introduce it from the rear with the kickstart lever in the upright position. If mistakenly installed with the nut towards the rear the pin will foul the footrest.

Removing Outer Gearbox Cover

WS Man Section D1, page D3

  1. Off the pipes/mufflers
  2. Off engine mounting plate (or footrest)
  3. Slack clutch cable, remove from hand lever, then gearbox
  4. Engage 4th gear (for loosening/tightening nuts later)
  5. Remove case screws and domed nuts
  6. Depress kickstarter lever slightly - to allow kickstart quadrant to clear inside top of gearbox
  7. Tap cover w. plastic mallet until free

    In 2015 I gently tapped in long thin knife blade to open the outer cover. Then tapped cover and wiggled - pried? Bad Boy!

  8. WSMan: "Gearchange pedal should be carefully raised then depressed, to control the release of the plungers and springs from the gear change quadrant"

Replacing Outer Gearbox Cover


Photo icon Posidrive screw locations in outer gearbox cover
  1. Apply jointing compound
  2. Turn kickstart pedal halfway down (its operational stroke)
  3. Offer cover to gearbox
  4. Check that kickstarter returns

Removing Inner Gearbox Cover

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Parts iconFig.9 Gearbox inner cover

Removing the Inner Cover & Dismantling the Gearbox

  1. Select 4th gear
  2. Remove gearbox outer cover (see above)
  3. Remove right engine plate
  4. Using rear brake, remove nut holding kickstart pinion ratchet
    (If transmission is already dismantled, a Tool icon clutch locking tool will work too)
    Note: alternatively, leave the kickstart nut in place and remove the mainshaft (below) and inner cover as a unit. Then you'll be all ready to reassemble the gearbox using Hugh Hancox's method.
  5. Dismantle transmission, see Dismantling Transmission above
  6. Remove gearbox inner cover
    1. Remove camplate indexing plunger and spring (3/4" socket)
    2. Remove oil lines from oil pipe junction block
    3. Remove junction block bolt (1/2" socket w extension)
    4. Remove bolt 21-1907 (Ref#20 Fig.7 #7) (7/16" socket)
    5. Remove Posidrive screw 14-6608 (Ref#22 Fig.7 Page 25 #7) (Posidrive)
    6. Remove allen head screw 14-7023 (Ref#23 Fig.7 #7 (.2335")
    7. Tap 'ear' w plastic mallet
    8. Withdraw cover slowly, using finger to keep the layshaft from coming out
  7. Remove gear selector fork spindle and then the forks (don't lose the 2 rollers)
  8. Remove main shaft, followed by
  9. Layshaft and gears
  10. Thrust washers
  11. Plunger carrier & camplate
  12. Gearbox sprocket nut and sprocket Tool icon (1 11/16" socket)

Inspecting the Gearbox Components

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Layshaft End Play

Although the manual doesn't give any spec, there seems to be a consensus on that layshaft end play should be around .005". By general agreement, it's not critical as long as there is some.

Can't see myself using either of these, but just in case, for future reference: two possible methods to gauge end play.

Gearbox Sprocket

Be sure to give the gearbox sprocket a good inspection for tooth wear and for 'hooking' of the teeth.

Gear Cluster Illustration ('69 T120R)

Illustration of Triumph layshaft and mainshaft gear cluster with part numbers and descriptions

Gears, Shafts, Bearings, & Bushes('69 T120R)

Exploded diagram of Triumph gearbox showing descriptions and part number of bearings, bushings, shafts, and gears for a 1969 Triumph T120R 650 motorcycle

Replacing Gearbox Inner Cover Bearings

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Drawing and description of replacing the layshaft bearing in the inner cover of a Triumph 650

Replacing Mainshaft Bearing in Inner Gearbox Cover

(Mainshaft ball journal bearing S35-7 - 3/4 x 1 7/8 x 9/16")
  1. Cool the mainshaft bearing
  2. Thoroughly heat inner gearbox cover
  3. Fit the mainshaft bearing (S35-7) (Tool-Z15)

Removing/Replacing Mainshaft and Layshaft Bearings in Gearbox Casing

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The gearbox casing holds two bearings:

Removing Mainshaft & Layshaft Bearings from Casing

I've read that these bearings can be difficult to remove, but in 2016 they both came out very easily without even heating the case.

From the primary chaincase side, I used a five-inch long 3/8" drive extension to drive out the layshaft closed end needle roller bearing (57-1606). Access to the bottom portion of this bearing is blocked by the primary chaincase, but I used the extension to tap on the bearing's top, left, and right hand sides. The bearing moved a little with each blow and it took less than a dozen shots before the bearing exited into the gearbox (and across the shop).

The mainshaft high gear bearing (50-0448) is driven out from the inside of the gearbox. I used a 1/2" drive extension and a 1 1/16" deep well socket. Again, the bearing moved easily with each solid blow and it took about ten hits to remove it entirely.

Replacing Mainshaft & Layshaft Bearings in Gearbox Casing

The first two times I replaced gearbox bearings I did it 'Hughie Hancox style': a torch and a hammer with drift. In 2018 this method wasn't working for me at all, and after scrapping the DS needle bearing I enlisted the help of Bob St-Cyr. After watching Bob press them in using a 50-ton industrial hydraulic press I am converted - no more bludgeoning bearings for me!

In order to press in the DS needle bearing I made a wooden base for engine on the primary side: Photo icon Engine Base

Replacing High Gear Ball Journal Bearing (57-0448 - 1 1/4 x 2 1/2 x 5/8")

When heating up the gearbox casing I used the non-contact infrared thermometer to take the guesswork out of attaining a 200 degree temperature evenly.

An indispensable trick was to use the old mainshaft as a "stick" to line up the large mainshaft bearing (57-0448) squarely with it's housing in the gearbox casing ( Photo icon Photo). Once it was started squarely I used a large, heavy drift against the outer race to drive home the bearing (Photo icon mainshaft bearing housing and drifts).

Don't forget to fit the circlip.

High gear bearing oil seal, open side to the bearing - tap it all around (like 25-30 times) with a ball peen hammer (beat the sucker in!).

Replacing Layshaft closed-end needle roller bearing

The specially shouldered drift I had made for layshaft needle bearing 57-1606 wasn't exactly right to automatically ensure the bearing's correct protrusion (.073-.078") above the gearbox casing, but I went slowly a little bit at a time and it worked out.

I marked the position of the thrust washer locating peg on the casing with a permanent marker to make it easier to align the matching hole in the thrust washer while installing the mainshaft.

Insure that the bearing lip is below the face of the bronze thrust washer.

Replacing High gear and drive sprocket

  1. From the inside of the gearbox, insert high gear through the bearing and oil seal.
  2. Push on sprocket with drop of oil where the flange runs in the oil seal.
  3. Place the case over an open vice, sprocket down, and use a 'suitable drift' (think big) to drive the sprocket all the way onto the high gear.
  4. Fit tab washer and large sprocket nut.
  5. Tighten the nut

    Note: Neither shown nor quite clear to me how he does this as the case is not in the frame and therefore can't be held by the chain and rear brake.

  6. Replace and tighten camplate plunger holder.
  7. Replace and tighten gearbox drain bolt.

Installing Gear Cluster

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WWW icon Side-by-Side Comparisons of Three Methods: WSManual, Hughie Hancox, & Haynes
WWW icon Hughie Hancox Method: Step-by-Step with Photos Illustration of Triumph 650 gearbox assembly with descriptions of parts

I've used several methods to assemble and install the gear cluster and in my experience Hughie Hancox's method is hands down the easiest, surest, and fastest way to do the job.

However you assemble, don't forget to seal the shifter fork shaft and the gearbox sprocket if you expect to not have oil leaks. Seal the shifter fork shaft because its drilling goes all the way through the casing. Permatex and Hylomar have both worked well for me. And keep in mind that after the gear box sprocket is installed, the shifter fork shaft drilling cannot be reached.

The layshaft thrust washers are another potential problem area. For starters, don't forget to include them in your assembly. During my first gearbox reassembly I left out the drive side thrust washer and had to take everything out and start over. I know others who have done the same.

The other important thing about the layshaft thrust washers is to be sure they are well installed over their locating pegs and that they don't fall off during assembly. A good smear of heavy grease helps.

During my first gearbox adventure I ended up reinstalling the gear cluster five times, and the transmission twice. The first time I put the cluster in it took just under two hours. The fifth time it took less than three minutes.

In 2015 I tried three different ways to install the gear cluster. I found the WS Manual method (see Method 3, below) of installing the gear cluster as a unit to be the easiest. I made one variation, and that was to index the quadrant and camplate in 1st gear and not in the neutral between 2nd and 3rd as suggested by the WS Manual (see Indexing Camplate & Quadrant below.

In 2016 I used Hughie Hancox's DVD method after making a couple of dry runs and seeing how easy it was. The one deviation I made was that I did not pre-install the mainshaft and kickstarter assy in the inner cover the way Hancox does on the CD. Instead I inserted the mainshaft by itself before putting on the inner cover and then the kickstarter parts.

The next time I'd be inclined to try the pre-assembly method simply to avoid having to torque the kickstarter nut (45lbs) from the right side while trying to hold down the brake on the left side. With pre- assembly, the nut can be torqued (45lbs) while the shaft is held in a vise.

Four Variations on Gear Cluster Installation

Method 1: Juggling

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  1. Install inside layshaft thrust washer using heavy grease
  2. Install camplate and orient as shown opposite
  3. Insert mainshaft
  4. Install mainshaft gears
  5. Install rollers on selector forks using heavy grease
  6. Install mainshaft selector fork (the longer of the two selector forks)
  7. Push mainshaft selector fork to rear until roller drops into camplate
  8. Possibly, use selector fork rod to manipulate/position/hold mainshaft selector fork
  9. Install layshaft
  10. Install layshaft gears
  11. Install layshaft selector fork (shorter of the the two selector forks)
  12. To allow it to fit in and for its roller to enter the camplate channel, back out the mainshaft/gears/fork selector components to provide sufficient clearance

Illustration of Triumph gearbox camplate positioned in neutral between 2nd and 3rd gears

Method 2: Juggling

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  1. Hold layshaft thrust washer in place with grease
  2. Install the camplate and position as shown in Service Bulletin
  3. Install mainshaft into gearbox
  4. Slide gears onto mainshaft
  5. From the bottom, put mainshaft gear selector (inc. roller) into its position on top
  6. Temporarily hold mainshaft gear selector in place with the gear selector rod
  7. Assemble layshaft with gears and gear selector outside gearbox
  8. Place the assembly on the bottom of the gearbox
  9. Gently work the layshaft assembly forward until the gear selector rod blocks further progress
  10. Hold mainshaft gear selector in place with a finger while removing the rod and replacing it with a very long, slender screwdriver
  11. Now work the layshaft and layshaft gear selector (with roller) into place
  12. Lift the layshaft and introduce it into the Torrington bearing at the far end
  13. Holding gear selectors in place with fingers, remove the screwdriver and re-insert the rod
  14. Insure that outboard layshaft thrust washer is in place
  15. Put low gear into place
  16. Put on inner cover while positioning the quadrant as shown in Service Bulletin

Illustration of Triumph gearbox camplate positioned in neutral between 2nd and 3rd gears

Method 3: Workshop Manual Variation

When I re-assembled the gears for the fourth and final time I used the method shown in the WS Manual, i.e. introducing both mainshaft and layshaft with all their parts and the shifting arms as a unit. With enough patience it does work. While the WS Manual shows the mechanic inserting the entire assembly without the rod upon which the shifter arms travel, I achieved assembly with the rod inserted through both shifting arms.

When inserting the cluster, first tip the cluster clockwise a bit to get the roller on the mainshaft gear shifter into the camplate. Then, going in further, tip the cluster counter-clockwise to get the layshaft gear shifter's roller into the camplate. The last time I did it the whole thing took less than three minutes.

Method 4: Hughie Hancox

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Hancox assembles the layshaft, layshaft gears, and mainshaft gears in situ before inserting the mainshaft, already installed in the inner cover, through the mainshaft gears.

As already mentioned, I find this method best of all and I've laid it out, step-by-step, with photo illustrations for those interested.

Thrust Washer Locating Pegs

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The thrust washers at either end of the layshaft are held stationary by hardened steel locator pegs in the casing that match holes in the thrust washers. Stuff happens and the pegs get ground down. Here are some descriptions of the problem with details on replacing damaged pegs.

When the Bonnie's locating peg for the DS thrust washer became damaged, I took the engine to Bob St-Cyr and he fabricated a jig which he used to drill anew hole for a replacement peg. Photo icon "Locating peg repair"

Indexing the Camplate & Quadrant

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WWW icon "Camplate & Quadrant Indexing" Three methods, complete descriptions & photo illustrations

Indexing the gearbox camplate and quadrant ensures that when the inner cover is pushed on, the camplate gears and quadrant gears mesh in the correct position relative to each other.

Indexing can be accomplished with the camplate set in any one of three positions:

For complete details and photo illustrations, click on the "Camplate & Quadrant Indexing" link just above.

Replacing the Inner Cover

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Note: On machines with a Norton oil filter head on the downtube, be sure to install the lower forward engine mounting bolt through the back of the inner cover before putting the cover in place. If not, the filter's mounting bracket prevents installation of the bolt from the back, and if the bolt is installed head out, the protruding portion of the bolt on the inside will interfere with the oil lines.

Sealing Inner/Outer Covers

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WWW icon "T100R gearbox assembly sealant"

I've had good luck sealing inner and outer covers using Hylomar Blue. Hylomar never hardens so it's easy to pull off the covers later. Excess Hylomar also cleans up easily, a rag and friction removes most of it and metal polish takes off whatever residue is left in a jiffy.

Gearbox Tear-down Notes

The Fuel System

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Gas tank


Icon for manual Workshop Manual (1969 650cc Twins) Section E1: Removing and Replacing the Fuel Tank
Parts iconFig.22 Gas tank
WWW icon "Bruce Hamilton: "FAQ: Automotive Gasoline" (inc. bibliography)
WWW icon "How to protect the petrol tank"
WWW icon "Best Tank Sealer"
WWW icon "Triumph paint thread" R Moulding's excellent paint thread, illustrations and discussion
WWW icon "Triumph Bonneville Paint Schemes 1959-1970" John Healy via Rask Cycle
WWW icon Tips on installing knee pads on gas tank
WWW icon "Stepless Ear Gas Line Clamps"

When securing the gas tank, I always begin by tightening the rear mount first. If the front nuts are started first it makes the gas tank lift up in back. I think that's why on so many bikes the threads in the frame for the rear tank mount are stripped. That happened to my brand new 1966 Bonneville, and both of the used Bonnies I've bought came with stripped threads.

Now I use a large tie-wrap over the tank's rear mounting tab (bolt and all rubber parts in place) and through the sidecar mounting hole. Again, I begin with the tie-wrap in back and then proceed to tighten the front mounts.

The front tank mounting stud on Bonnie's timing side came loose once. Leon Goldick of Montreal, who made such a great paint job on Bonnie's tank did the repair and touch-up.

The question often comes up, what to do with the gas tank over the winter season? I confess that I usually get around to draining the tank by February and then leave it empty, but this is not the greatest strategy, especially with ethanol fuel which attracts moisture - the better to rust the inside of the tank. See the link "How to protect the petrol tank" just above for a discussion of what guys do with their tanks in the winter.

Gas Line

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After reading all the way through this WWW iconTriumphRat fuel line thread I've decided to switch from classic look reinforced plastic lines to rubber hose for reasons of safety. The plastic lines frequently leak, and in case of a fire they melt, adding gas to the fuel.

When removing carburettors it is only necessary to disconnect the fuel lines from the gas taps. The carbs can then both be removed as a unit without disturbing the rest of the fuel line connections. Likewise, when tearing down the carbs, one can simply unscrew both banjo bolts and remove them and the fuel lines as a unit.

Gas Taps

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The brass gas tap fuel line connectors shouldn't be so tight that they can can't be loosened by a few light raps with two or three fingers on a wrench. Avoiding over-tightening prevents the gas tap from turning and possibly breaking the seal to the tank.

Sealing Gas Taps

WWW icon BritBike Forum Discussion: "Sealing Gas Taps", Discussion of various sealing washers and methods of making leak-free connection between gas tank and gas taps. In addition to some good insights, this thread includes some funny ripost, some blowing off of steam, and, briefly, some party-line-like communication.


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Icon for manual Workshop Manual (1969 650cc Twins) Section B7: Concentric Carburettor Type 900 (Illustration)
Icon for manual Workshop Manual (1969 650cc Twins) Section B8: Removing and Replacing Carburettors
Icon for manual Workshop Manual (1969 650cc Twins) Section B9: Stripping and Reassembling the Carburettor
Icon for manual Workshop Manual (1969 650cc Twins) Section B10: Inspecting the Carburettor Components
Icon for manual Workshop Manual (1969 650cc Twins) Section B11: Carburetter Adjustments
Icon for manual Workshop Manual (1969 650cc Twins) Section B12: Twin Carburetter Arrangement
Manual icon Amal "Hints & Tips for Amal Mk1 Carburettor"
Manual icon Triumph Service Bulletin #2/73 "Checking & Adjusting the Amal Concentric Float"
Parts icon Fig.31 Concentric 930
WWW icon John Healy: "Amal Concentric Carburettors" (2017)
WWW icon John Healy: "Tuning Your Carburettor" (2013)
WWW icon Jim Bush: "Bushman's Carb Tuning Secrets"
WWW icon "Bonnie carb jetting help needed" (reading spark plugs w. illustrations)
WWW icon "Amal manuals for Monobloc & Concentric (inc. Premier) carbs"
WWW icon Jeffery Diamond: "Super-Tuning Amal Concentric" (Advertisement for booklet)
WWW icon "Notes on Rebuilding the Mark-1 Concentric Carburettor"
WWW icon Richard Whatley: "Leaking Amal Carburettors"
WWW icon "Amal Concentrics, How they Work and Tuning"
WWW icon "Motor dies just as I take up throttle cable slack" Electrical or Carb? Informative thread
WWW icon "Pin gauges for needle jets" Long, informative thread on needle jets
WWW icon "Variations within the 930 Amal Concentrics" TR7RVMan describes Amal Mk1 & Premier differences
WWW icon TR7RVMan offers some good tips on cleaning carbs
Video icon YouTube Raber's Tech Tips, Episode 6: Triumph 1971 T120 Bonneville Amal Carb O-ring Installation

Random Notes

Carburettor O-Rings

The o-rings that fit between the carb body and the carb adapter (intake manifold) come in two sizes: one is thin and the other is thick. The thick ones seem a little too large for the groove in the carb body, and the thin ones seem a tiny bit too small.
When I got Bonnie from Frank Holmes he'd fitted her with thick ones and that's what I've always used. Stick 'em on with a couple dabs of grease and then carefully fit the carburettor to the studs on the adaptor. Then it's finger yoga putting on the rubbers, cupped washers, and nuts, all the while holding the carb ever so slightly off the adapter so the nuts will clear the casting around the ticklers. That o-ring didn't move did it?
Raber's made this excellent video in which Michael explains the thick and thin of it and shows us how to coax in the thick o-ring.
WWW icon YouTube Raber's Episode #6 Video
What I learned from the video is that while the thick o-ring is used solo, the thin one is used in conjunction with an insulating block (E2968) and a joint washer (NA43A). As we see by the next table, Frank updated Bonnie's thin o-ring/insulation block setup to the solo, thicker o-ring (70-9711) introduced in 1970.
WWW icon Triumph 650 Carb to Carb Adapter O-rings, Insulating Blocks, & Joint Washers
The thick ring reduces engine heat transfer by creating an air gap, and Rabers' says another advantage is that the thicker o-ring reduces the chance of warping the carburettor flanges with uneven or over-torquing. I'm still going to be very cautious of over-tightening those nuts. I have read that there should be .040" to .060" space between the carb flanges and the adapters, and I have found that to be a reliable guide in actual practice.

Amal Concentric 930 Cross-Section

Cross section drawing of an Amal Concentric 930 Carburetter

Amal Concentric Carburettor Parts

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Manual icon Amal "Parts to Tune Up - Amal Mk1 Carburettor"

Summary of Carb Specs & Settings

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Main jet size220190
Needle position Up = richer22 (middle)
Needle jet size.106.106
Idle speed adjustment screw 1 1/2 out
Idle air adjustment
Screw out for leaner, in for richer
2 1/4 - 2 1/21 1/4 - 1 1/2

Mid-69 Concentric Modification

According to Bill Litant (BritIron mailing list), BSA made modifications to concentrics in mid-1969 to improve low and midrange performance. The correct parts match ups are:

  Needles Needle Jet Jet Holder
(pre-mid 1969)
2 9/32" long
One identifying ring
11/16" long 3/4" long
(post mid-1969)
2 21/32" long
Two identifying rings
13/16" long
7/8" long

Choke Assembly

I removed the chokes from Bonnie's original Amals and never installed them on the replacement Amals. I plugged the hole on top of the carbs with epoxy and it's held up for all the many years. Amal does make a blanking screw: Amal part number 4/137 (StuartMac).

Float Bowl Flooding

If a carburettor is flooding frequently or, worst case, overflowing fuel, it is likely due to either the float not rising (float holed and filled with gas or hung up on the float bowl gasket) or the float needle not seating well (needle worn out or dirt lodged beneath it).

WWW icon StuartMac's easy method to pinpoint float bowl problem

Another possibility is that the fuel level is simply adjusted too high. That adjustment can theoretically be made by lowering the float needle seat. Tricky, but here's the Triumph Service Bulletin to guide you:

Tool icon Triumph Service Bulletin #2/73: "Checking & Adjusting the Amal Concentric Float"

On the other hand, it would be easier to replace plastic bowls with Amal 'stay-up' floats. In addition to being impervious to the effects of ethenol, 'Stay-ups' also have adjustable tangs holding the float needle in place and can be bent up or down.

Float Bowl Leaking

Fuel leaks from the float bowl are sometimes the result of over-tightening the float bowl screws which causes the bowl to warp. If the leak occurs after changing the gasket, or after the bike has been sitting for a period of time with no fuel in the bowl, the leak may cure itself after the gasket has soaked and swelled up sufficiently to make a good seal. I have also stemmed this kind of leak with some Hylomar smeared on both sides of the gasket.

The official remedy is supposedly to flatten the float bowl by gently rubbing it on a sheet of very fine abrasive paper over a completely flat surface. Be aware, though, that removing an excessive amount of metal will affect the height of the float and float needle.

Assembling Cable, Spring, Air Slide, & Needle Jet/Clip

When refitting cable to air slide, don't try to compress the spring against the carb cover, away from the cable end. Instead, pinch the exposed (slack) wire cable with finger and thumb and push the cable (and spring) towards the bottom of the air slide until the cable pokes through the other side. So, compress the spring against the air slide, not the cover.

When installing the needle jet and it's clip - that's when to scrunch the spring up against the carb cover, gently hanging the bottom end over and outside the carb body while you drop in the needle and clip.

Cleaning the Pilot Jet

I've been using a guitar string to clear the idle jets, but some say this just pokes the dirt back upstream where gas will eventually wash it back down to the jets. John Healy says to use a#78 drill through the pilot air screw hole to pull the dirt out of the jet and downstream:

"Use a #78 (.016") drill mounted in a piece of hobby brass tubing works the best. If you twirl it between your thumb and fore finger as you offer it, it pulls the swarf downstream of the jet to be washed away by the flow of fuel."

Tuning the Mk1 Concentric Carburettor

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Icon for manual Workshop Manual (1969 650cc Twins) Section B11: Carburetter Adjustments
Manual icon Amal "Parts to Tune Up - Amal Mk1 Carburettor"
Manual icon Amal "How to Tune - Amal Mk1 Carburettor"
Manual icon Amal "Tuning Twin Carburettors - Amal Mk1 Carburettor"

Adjusting Low Speed Mixture & Idle Speed & Synchronizing Carburettors

The Workshop manual explains how to sync carburettors in Section B12: Setting Twin Carbs but forgets to mention final adjustment of cable adjusters.

The entire routine for adjusting low speed mixture, idle, and synchronizing:

  1. Slack cable adjustors off completely
  2. With one plug off, start and adjust air and idle screws for good idle
  3. Perform same adjustment on opposite cylinder, matching idle RPM of first
  4. Start on 2 cylinders and adjust both idle screws out the same amount
  5. Open cable adjusters, one at a time, until idle just starts to rise
  6. Back off one turn
  7. Using chopsticks, check to see that both slides lift at the same time

It's a good idea to open the twist grip and then let it snap shut once or twice in between checking new synchronization settings for the cables.

Initial Synchronization of carburettors (no Low-speed adjustment)

See Amal Mk1 tuning links.

  1. Remove air cleaners
  2. Back idle adjustment screws all the way off
  3. Turn idle screws back in until they just touch throttle slides
  4. From there, screw them in 1.5 turns
  5. Adjust cables for synchronization

Mid-Range Tuning

See Amal Mk1 tuning links.

The next two sections talk about "8-stroking". If you're not familiar with the term, John Healy WWW icon describes it well on

WWW icon Gavin Eisler offers this sage tuning tip on "At half throttle, if acceleration could be better, no 8-stroking, clean running but slow to pick up maybe spits back as the throttle is opened, that's lean at the needle jet or needle position, try lifting the needle one notch..."

High Speed Tuning

See Amal Mk1 tuning links.

A plug chop is one way to determine the correct main jet size, but there is an alternative. If engine power is flat above 3/4 throttle in top gear, begin increasing the main jet by two sizes at a time until the engine '8-strokes', then go down two sizes. So, to check if installed main jet is correct size, put in a jet two sizes up. If the engine '8-strokes' above 3/4 throttle, the smaller jet is the correct size.

Trouble-shooting Carburation - reading the signs


Manual icon Amal "How to Trace Faults - Amal Mk1 Carburettor"

World Wide Web icon Follow these informative trouble-shooting discussion links for better understanding.

Air Cleaners

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Icon for manual Workshop Manual (1969 650cc Twins) Section B6: Removing and Replacing the Air Cleaners

Installing Air Cleaners

When using paper air filters, both air cleaners can be screwed on/off intact, but when using wire and gauze filters (thicker than the paper ones) the right-hand unit must assembled/disassembled in place due to interference from the foreword edge of the oil tank.

  1. Install the assembled air cleaner, cover, and retaining clip/screw (or assemble in place if necessary)
  2. Before threading the assembly on all the way, loosen the securing screw for the clip
  3. Now thread the filter onto the carburettor until it just stops
  4. Holding the adapter there, rotate the (loose) cover and clip until the cover is aligned properly
  5. Now back off the adaptor along with the cover and clips until you can tighten the securing screw
  6. Screw the entire assembly back on all the way and give a gentle twist to tighten it to the carburettor

Air Filters

I prefer the wire gauze units because they are reusable. I used to wash them in kerosene, but more recently I've been washing them with hot water and dish washing detergent.

I like the idea of using a water-based degreaser and then rinsing in hot water, as suggested by Rod Rocket on

Control Cables

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Parts iconFig.28, Cables
WWW icon Mike Partridge: Control Cable Tips
WWW icon Tri-Cor Cables, England Cable Chart

Lubricating Cables

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Lube all cables with 10W oil (WS manual calls for the elusive 20W) Taping the spout of an oil squirter can to the cables gives good results.

Throttle Cables

Bonnie is using standard 43" cables for US bars.

Cable Routing


New throttle cables. T.S. cable crosses to D.S. through frame and both cables pass through fork on the D.S.


New throttle cables: installed, they measure 42 3/4" (sleeving), or 45" (cable). These are for the new, low handlebars.

T.S. throttle cable crosses to D.S. through space in frame and then both cables pass to left of steering head and NOT through the hole in the headlamp bracket. Seems to give very good slide response.

Neither carburettor has any nipples between them and the cables at this time - perhaps when the new cables have stretched out.


Throttle cables installed without the former cross-over.

Both carburettors now have two nipples between the cables and the carburettors.


Throttle cables originally "crossed over", i.e. the outboard cable on the twist grip went to the D.S. carburettor.

Throttle Twist Grip

Use oil and not grease to lubricate the twist grip. Grease is too thick and the throttle will 'hang'.

Clutch Cable


Currently the clutch cable makes an arc and passes through the space between the gas tank and the gas tank bracket on T.S. and resting just on top of the forward oil line acorn nut.

Formally passed to the left hand side through the triangle in the frame beneath tank to rear of coils

Speedometer and Tachometer

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Parts iconFig.33 Speedometer and Tach
WWW icon Smith's Instrument Repair Resources


Disassembly & Removal of Tachometer Drive Gearbox

Parts Reference: #7, Fig.33 Page 73 (link just above).

  1. Remove tachometer cable
  2. Remove the end cap (70-5759, Ref.#21)
  3. Remove the driving gear (70-5157, Ref.#20) by depressing the kickstarter smartly
  4. Remove LEFT-HAND thread securing screw (70-9332, Ref.#17) using a (7/16") (13mm) (3/16W) thin-walled socket
  5. Tach gearbox will now separate from crankcase

After removing the gearbox from the crankcase always replace Sealing washer (70-7351, Ref.# 33 - same part used for gas taps) as well as o-rings as required.

Lubricating Tachometer Cable

See speedometer cable below.

Lubricating Tachometer Drive Gear

Unscrew tach drive plug and add grease after cleaning out as much old grease as possible. When plug is screwed in, excess grease will be expelled at cable connection to drive unit.

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WWW icon - Crankbuster's "Smiths Magnetic Speedo". Crankbusters Animated assembly of Smiths Magnetic Speedo.

Speedo Cable

Cable Lubrication

Formally I lubricated speedo and tach cables with light oil using a rag and avoiding the closest 6-8" to the speedo head.

However, Andy Hansen of Vintage British Cables advised me against using oil and recommends grease instead, because the oil can "corkscrew" its way up the inner cable and into the instrument.

After inspecting a new speedo cable I purchased from Andy I wasn't sure if it was adequately pre-lubricated as I could just barely detect a light coat of grease. I emailed Andy and he replied that his cables are indeed pre-lubricated and ready to install. This set off all kinds of bells and bright lights - I have been over-greasing the cables!

So, apply a very light coat of grease after unscrewing the collet beneath the speedo/tach head and withdrawing the inner cable. When replacing the cable be sure the ends are properly seated at both the speedometer gearbox and speedo head.

Speedo Gearbox

WWW icon - Crankbuster's "Smiths Speedo Drive Gearbox". Animated assembly of speedometer gearbox showing its construction. Tip of the hat to "BigSky" on

Using a grease gun with the appropriate fitting, periodically add grease to the gearbox.

Replaced Taiwanese Smith pattern with another Taiwanese Smith Pattern from MAPCycle 2014 when putting rebuilt speedo into service. Have original Smith gearbox on hand.

Speedometer Problems

WWW icon - Don's informative post on trouble-shooting & fixing speedometer cable problems

Many speedometer problems are cable-related. Too much or too little cable lubrication, or incorrect inner cable length (too short or too long) top the list of possibilities. Using an electric drill (very low speed only!) to drive the cable or the speedometer head can sometimes help in isolating the problem.


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Icon for manual Workshop Manual (1969 650cc Twins) Section G1: Removing the Telescopic Fork Unit (Covers Handlebars)
Parts iconFig.18 Handlebar mounting, steering damper
Parts iconFig.27 Handlebars, control levers, steering damper
WWW icon (BCS) BCS's Handlebar Chart with Dimensions

Handlebar Shock-Absorber Mounting

For the handlebar shock-absorbing mounting to work properly, the parts must be installed in the correct order and with the hemispherical washers in the correct orientation, i.e. the hemispherical sides facing each other.

It is also important that the hemispherical washers have indents around their inner hole. The indents match the shoulders on the shanks of the eye bolts and if they are not present the eye bolts can be stressed to the point of breaking. (John Healy). Illustration of correct assembly of a Triumph shock-mounted handlebars

The correct order of the parts is listed below and shown in the figure to the right.

  1. Hemispherical washer (flat side up)
  2. Distance piece
  3. Steady rubber
  4. Cup
  5. Bonded bush in upper steering yoke
  6. Hemispherical washer (flat side down)
  7. Nylock nut

Safety Note: If the eyebolt makes contact with the head lug, see
Image of Triumph service bulletin #306, Triumph Service Bulletin #306: flexible handlebar mounting "Flexible Handlebar Mountings on 650s".

Removing Handlebar Mounting Bonded Bushes from Upper Steering Yoke

  1. (Remove upper steering yoke - but not if it can be avoided)
  2. Slip 1/2BS socket over 4 1/2" x 5/16" hex head bolt with drive end of socket towards bolt head
  3. Insert the bolt through the center of the bonded bush from either top or bottom of upper steering yoke.
  4. Slip 5/16BS socket over end of bolt with drive end of socket facing away from the upper steering yoke
  5. Install a nut onto the bolt (if required, use washers as spacers)
  6. Secure the bolt's hex head in a vise
  7. Align the 5/16 BS socket with bonded bushing's outer sleeve
  8. Tighten the nut until the bushing slides out

Use similar method to install new bushings.

Handlebar Grips

One suggestion that pops up on forums for keeping handlebar grips on is hair spray. I tried hair spray once and quickly learned how dangerous that idea is. Hair spray seems to hold ok as long as everything is dry, but the moment there's the slightest amount of water around it becomes super-slippery - so slippery that light pressure from two fingers will slide a grip right off the bars.

The old school method was friction tape - not electricians' tape, but cloth tape. Wrap the tape on the bars and then smack the grip over the tape. But perhaps the best solution is THREE BOND Griplock #1501C. Pricey, but do you really want your handgrips to slide off while you're tooling down the road in a rain shower?


Shock Absorbers

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Icon for manual Workshop Manual (1969 650cc Twins) Section E5: Adjusting Rear Suspension
Parts iconFig.13 Swing arm, rear shocks
WWW icon "Shock absorber replacements" inc. comments on Emgo, Hagon, Ikon, Fournales

Disassembling Shocks

Dealing with the split ring clips at the top is much easier with two sets of hands.

Installing Shocks

When replacing the shock absorbers, don't force the mounting bushings into place from the rear of the frame bracket or from directly beneath the mounting holes for the shocks. Instead, insert the bushings from beneath the spare hole in frame bracket and then slide them to the rear and into place. May need a few little plastic mallet taps, but you should not have to beat on them if you take the right approach.

Outside to inside, #7 shows bolt, plain flat washer, spring lock washer, plain nut.

Replaced with new units in 2013.

Ok for bushings to be pushed off-center apparently.

#7 shows only one shock absorber bolt, and it appears head out. On the brake side, however, I've put the nut on the outside on the bottom so the bolt doesn't scrape on the brake drum cover.

Front Fork and Steering Head

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Icon for manual Workshop Manual (1969 650cc Twins) Section G: Front Fork (TOC)
Parts icon Fig.17 Front Fork
Photo icon  Front Fork Components
Video icon YouTube Raber's Tech Tips, Episode #2 - Triumph 500 / 650 Front Axle Widths
Video icon YouTube Raber's Tech Tips, Episode #5 - 1967 Triumph TR6 Front Fork Disassembled

Note: Triumph used three different width axles: 1) pre-unit, 2) unit through '68, and 3) unit '69 on. This table shows the differences between earlier and later unit model fork and axles:

  Unit, pre-'69 Unit, '69-on
Fork Legs Center to Center 6-1/2" 6-3/4"
Axle Brake Plate Thread 20 tpi 3/4" BSC 20 tpi 3/4" UNEF (Extra Fine)
Wrench Size 1.01"AF
1-1/16" AF a fair fit
or 5/8" BS
or 9/16"W
1-1/8" AF

Steering Damper


Parts icon Fig.18 Steering Damper
Parts icon Steering Damper Fitment by Years
WWW icon Steering damper

In 1969, only the TR6C came equipped with a steering damper. I found the dampers on my '66 Bonnevilles to be both useful and aesthetic so I retro-fitted one on Bonnie. Very good on bad roads and windy days, just be sure to loosen it when you get into town!

My theory is that wind affects a down-road trajectory not so much by its action on the bike, but on the upper body of the rider. The wind pushes the rider, whose shoulders move, and the motion is transmitted to the handlebars. The steering damper virtually eliminates the effect.

When I retro-fitted a damper to Bonnie I neglected to fit 'locating pin' 97-2107, which, I learned recently from TriumphDave's post, prevents the sleeve nut from being loosened so far that it falls off. Hats off to Dave, I'll soon have one on order.

Steering lock

The steering lock cylinder is held in place by a counter-sunk set-screw. The set-screw hole is covered over by a plug which must be dug out before removing the set-screw and lock cylinder.

Front Fork Gaiters

The gaiters can be removed and replaced by removing the front wheel and fender. When installing new gaiters this way the 'sticking point' can be getting the tops of the gaiters past the dust excluder sleeve nuts. A method that works well is to dig the tips of both thumbs right into the gaiter just below the "collar" at the top and push them right on.

Removing Front Fork As a Unit

Remove as a unit to maintain steering head bearings.

  1. Drain fork oil (see "Draining Fork Oil")
  2. Remove front brake cable
  3. Remove split clamps and front wheel
  4. Fender and fender braces can remain in place
  5. Disconnect battery
  6. Remove headlamp shell and bungee to frame
  7. Remove throttle grip and clutch cable
  8. Remove handlebars
  9. Remove steering damper
  10. Slacken seated nut on top steering yoke pinch bolt
  11. Remove fork stem sleeve nut
  12. Remove left and right stanchion tube cap nuts
  13. Support front fork... it's coming off!
  14. Use plastic mallet to tap underside of upper yoke
  15. Catch steering head ball bearings - especially the bottom ones

Removing Front Fork Legs Separately

Remove separately to maintain fork - oil seals, etc.

  1. Disconnect battery
  2. Drain fork oil (see "Draining Fork Oil")
  3. Remove steering damper
  4. Remove front brake cable
  5. Remove split clamps and front wheel
  6. Remove front fender and braces
  7. Remove headlamp shell (bungee to frame)
  8. Remove throttle grip and clutch cable
  9. Remove handlebars
  10. Remove left and right stanchion tube cap nuts (Tool icon Stanchion cap nuts wrench))
  11. Slacken lower yoke pinch bolts
  12. Spread lower yoke slots with chisel or screwdriver
  13. Thread service tool Z161 stanchion tube puller into stanchions and drive them free
  14. Remove left and right top fork covers

Dismantling Front Fork

  1. Remove cork washer and gaiter
  2. Remove spring abutment and spring
  3. Remove dust excluder sleeve with Tool icon Dust excluder sleeve nut wrench
  4. With lower leg in vise use a sharp pull to withdraw stanchion
  5. Remove bearing nut and withdraw shuttle valve
  6. Remove lower bearing
  7. Remove pvc damping sleeve (note built-up end is down)
  8. Remove circlip to separate shuttle valve from bearing nut

  9. Remove plain washer from top of dust excluder sleeve
  10. Turn sleeve upside down and drive oil seal out with drift
    (have replacements on hand, seals are ruined)
  11. Place sleeve in (wood-faced) vice upside up and clamp loosely
  12. Use drift to drive out upper bearing and plain washer
  13. Remove "o-ring" from groove inside sleeve (renew)

  14. Manuals say the hex-base of restricters are recessed into bottom of lower fork legs - not on Bonnie
  15. Use speed wrench and extension with 5/8" socket to hold restrictor while using 1/4"drive 5/16" socket to remove flanged screw and aluminum (copper) washer

Replacing Fork Seals

I have replaced Bonnie's fork seals: May 2014/March 2007/May 2003.

Refitting Stanchion Tubes

Tool icon Use service tool Z161, stanchion tube puller to draw stanchion tubes into top lug.

Refitting Fork to Frame

With front fork removed as a unit.

  1. Hold ball bearings in place with grease
  2. Fit lower yoke and stem through frame and top yoke
  3. Use a short bungee cord over the frame and through the stanchion tube holes in lower yoke to keep the stem from dropping
  4. Place cupped dust cover over ball bearings on top
  5. Use stiff wire to hold down the cupped dust cover and prevent top ball bearings from escaping - over the cover and around the frame
  6. Fit top yoke over the stem, screw on fork stem sleeve nut (The new fork stem sleeve nut used with the steering damper was difficult to rotate inside the upper yoke so I tapped it into the yoke and then rotated the yoke to get the sleeve nut started threading on the stem and then used the 1/2" drive ratchet drive with a socket to tighten it down)
  7. When stem nut contacts the wire, back-off, remove wire, and then continue to adjust the sleeve nut
  8. Tighten sleeve nut ONLY enough to remove fork play
    (Check by pulling and pushing on ends of lower legs)

Aligning Front Fork

When replacing front wheel and axle, the front fork should be aligned as follows.

  1. With wheel and axle and axle caps in place, finger tighten the axle cap bolts on both sides
  2. Using 1/2" wrench or socket, tighten the axle cap bolts on one of the axles
  3. Compress the front fork as much as possible
  4. Tighten the axle cap bolts on the side where they are finger tight

Steering Head

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WWW icon Part numbers for cones & cups to replace loose bearings
WWW icon Lowbrow Customs Tapered roller bearing conversion kit
WWW icon CBS description of 2-piece drift for installing steering head bearings

Refitting Without Fork

(For refitting with fork, see Refitting Fork to Frame just above)

  1. Hold ball bearings (20 top and 20 bottom) in place with grease
  2. Fit lower yoke and stem through frame and top yoke
  3. Use a short bungee cord over the frame and through the stanchion tube holes in lower yoke to keep the stem from dropping
  4. Place cupped dust cover over top ball bearings
  5. Use stiff wire to hold down the cupped dust cover and prevent top ball bearings from escaping - over the cover and around the frame
  6. Fit top yoke over the stem, screw on fork stem sleeve nut

    (The new fork stem sleeve nut used with the steering damper was difficult to rotate inside the upper yoke so I tapped it into the yoke and then rotated the yoke to get the sleeve nut started threading on the stem before using 1/2" drive and socket to tighten the nut)
  7. When upper yoke contacts the wire, back-off, remove wire, and then continue adjusting the sleeve nut
  8. Tighten sleeve nut ONLY enough to remove fork play
    (Check by pulling and pushing on ends of lower legs)

Front and Rear Axles

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Parts icon All Front & Rear Axle Retainers, Support Rings, and Dust Covers Illustrated
This photo shows the top and bottom sides of all grease retainers, dust covers, support rings, backing rings, and retaining rings on the front and rear wheel axles. It also includes dimensions, part numbers, and reference numbers.

Parts icon Front Axle bearings, covers, rings, and retainers
This photo shows the orientation of all parts on the front axle, including the dust cover, retaining ring, support ring, grease retainer, bearings, and circlip.

Parts icon Rear Axle bearings, grease retainers, and retaining and backing rings illustrated
This photo shows the assembly order of the rear axle bearings, grease retainers, retaining ring, backing ring, and speedometer gearbox.

Parts icon Rear Axle nuts and distance pieces
A photo showing the assembly order of the rear axle inner and outer nuts and distance pieces.

Front Wheel

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Icon for manual Workshop Manual (1969 650cc Twins) Section F: Wheels, Brakes, and Tires (TOC)
Parts icon Fig.19 Front Wheel
WWW icon Replacing Rims - Devon vs Central
Tool icon Wheel Bearing Locking Ring Wrench

Front Wheel Bearings


Photo icon Photo & Drawing: Front Wheel Axle Parts


[Replaced Bonnie's FWB May 2014 @60kmi (MAPCycle sealed bearings) & July 2007 @36kmi]

I disassembled the wheel and re-packed the bearings after cleaning them out with kerosene and compressed air.

The (cupped) grease retainer on the inside of the left-hand side was in backwards I think - the cavity was facing away from the bearing so I put both the retainers back with their cavities facing the bearing the way it appears to be in the parts manual.

Front Wheel Brakes

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Parts icon Front Brake Shoe Illustrated
WWW icon Tips on renewing and tuning vintage motorcycle brakes
WWW icon Stuart provides many details on various Triumph hub, anchor plate, & axle setups

Removing Front Brake

  1. Apply front brake using a tie wrap
  2. Use a 1 1/8 deep socket to unscrew the backing plate nut (RH)
  3. Pull out the backing plate assembly and note the position of the twin leading shoes (TLS)


When reassembling the brake, note that:

Replacing Front Brake

  1. When replacing the backing plate assembly, don't tighten the nut fully
  2. Center the shoes by lightly tapping the backing plate with a plastic mallet with the brakes slightly on
  3. If necessary, adjust the brake lever as the shoes become centered
  4. Undo the pin on the brake arm and pull the front shoe's lever until both shoes are snug
  5. If adjustment is required, loosen the locknut on the clevis joint and turn the clevis until both shoes are contact the drum equally
  6. Keep the shoes centered as you tighten the backing plate nut by applying the brake firmly

Adjusting Front Brake

From the WS Manual evidently:

  1. Slack off the brake cable at the handlebars to remove all tension on the linkage
  2. Remove the locking pin connecting the two cam levers together
  3. Apply both cam levers stiffly
  4. Adjust the link rod length until the loose end just fits into the other cam lever
  5. Re-insert the locking pin and tighten the locking nuts on the lever
  6. Make an adjustment at the hand lever for a slight slack in the cable
  7. When adjustment is complete, rotate the wheel rapidly in its normal direction
  8. With the wheel spinning rapidly, apply the brake hard to stop the wheel abruptly

But as always, there's more to it than that.

WWW icon Rancidpegwoman, the Village Idiot, and others divulge their best brake tuning secrets

Front Wheel Fender Brackets/Stays

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WWW icon StuartMacs tips on fitting the front fender stays to fork

The front wheel and tire can be removed without disturbing the fender and fender braces if the tire is deflated somewhat

The front fender brackets (Ref.5 in Fig.26 Fenders ) fit on the lower fork legs pointing forward with the bottom angle projecting upwards.

The bolts (Ref.23) which fix the stays to the brackets face nuts out (Ref.24).

Figure 26 (#7) doesn't show how the forward and center stays (Ref.2 and Ref.3) fit onto the fender brackets (Ref.5). They should both be fixed to the outside of the fender brackets Photo icon as shown here.

If the fixing bolts are hard to get through the stays and bracket, slacken the bolts holding the stays to the fender and then give the bolts a rap with the plastic mallet.

[The mounting hole for the bottom stay (Ref.4) in Bonnie's used replacement lower fork leg is threaded, so the bolt must be threaded in and out.]

Rear Wheel

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Icon for manual Workshop Manual (1969 650cc Twins) Section F: Wheels, Brakes, and Tires (TOC)
Parts iconFig.20 Rear Wheel
WWW icon Replacing Rims - Devon vs Central

Rear Wheel and Chain Guard

Removing Rear Wheel

Rear wheel must be raised (chain hoist or bike jack) for tire to clear fender when removing.

  1. Remove master link, secure ends of chain out of your way
  2. Loosen rear axle nuts
  3. Remove brake rod
  4. Remove torque stay
  5. Loosen rear bolt for chainguard and raise guard
  6. Pull rear wheel backwards until axle disengages from swing arm
  7. Unbolt two remaining bolts to remove chainguard

Replacing Chainguard

Parts iconFig.13 Chain guard

Install the chainguard first (loosely) and then install the wheel.

Putting self-locking nut (14-0702) on bolt (14-0113) fastening the front of the chainguard to the frame can be a huge pain. Try this:

  1. (Bolt 14-0113 must have been in place before fender was installed)
  2. Use tweezers or angled needle nose pliers to place washer over the bolt (Number 7 shows NO washer, though there is one on Bonnie)
  3. Put a "spacer" nut into a 7/16" socket, followed by nut 14-0702
  4. Using an extension as a handle, screw the nut onto the bolt

The bolt head is pretty well held in place by the fender for this operation, it only needs held with a wrench for the final tightening, at which time it is more easily accessed when the side panel is removed.

Alternatively, jam small metal chisel between fender and frame mount to make room for nut, held in place with fingers while threading on nut as above.

Note: installing this bolt and nut has been easier the last few times - perhaps because the stainless fender has become more 'relaxed'.

Replacing Rear Wheel

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When reinstalling the rear wheel the speedometer gearbox must be positioned so that the speedometer cable lines up straight with the swinging arm before tightening the inner axle nuts. This can be done with the wheel on the bike, but it requires a thin (3/4") wrench. I don't have such a wrench, so I align the speedo gearbox, center the brake shoes, and tighten the inner nuts before installing the wheel. Getting the speedo gearbox positioned correctly is pretty much trial-and-error.

  1. Place the wheel in position on the bike
  2. With the torque stay in place, rotate the speedo gearbox and take note of the position of the gearbox with respect to the torque stay stud on the anchor plate
  3. Remove the wheel from the bike and hold the tire upright with a bench vise
  4. Position the speedo gearbox positioned with the anchor plate as previously determined
  5. Tighten the inner nuts
  6. Reinstall the rear wheel and torque stay and check speedometer gearbox alignment
  7. Repeat as necessary
  8. Order thin 3/4" wrench

Centering Rear Wheel Brake Shoes

The rear wheel brake shoes should be centered to the axle to prevent the brakes from 'pulsing'. To center the brake shoes, apply the brakes while tightening the inner axle nuts.

The inner axle nuts can be tightened with the wheel in place but it requires a very thin 3/4" wrench. Since I don't have such a wrench, I center the brake shoes and tighten the nuts on the workbench this way:

On my Bonnie this results in the wheel turning very stiffly on the rear axle, but the stiffness disappears as the wheel is rotated. I've read that too much binding can result in damage to the bearings and that a shim should be added to give more clearance over and above that provided by the spacers.

Brake Torque Stay

Brake torque stay (ref 11 page 37) should go on before the plate for passenger foot peg and muffler bracket.

Both ends of torque stay are supposed to use the same nuts (14-0304)(3/8W) and spring washers (PCW73A), but on Bonnie one is thicker front) and one is thinner (rear).

The "C"-clamp on the torque stay adjusts the bottom of the chainguard with respect to the tire and the chain. It must be fit so that it rests ON TOP of the chainguard bracket to allow for adjustment. Bit of a PITA, but fitting the nut and bolt with the passenger peg and mounting plate removed is much easier.

Rear Wheel Bearings

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Photo icon Photo & Drawing of Rear Wheel Axle Parts
Tools icon Wheel Bearing Locking Ring Wrench

Replaced Bonnie's with sealed bearings from MAPCycle May 2014 60,000mi.

Rear Wheel Brakes

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Parts iconRear Brake Shoes Illustrated


Shouldered end of the rear wheel spindle goes to T.S. Seerear axle photo and illustration. Photo icon

If removing the brake cam lever ( Ref 32 Figure 20) from the brake cam post is difficult, try this:

  1. Remove S1-52 nut and S25-6 plain washer
  2. Replace the nut, leaving it somewhat loose
  3. Apply a bit of heat to the actuation arm
  4. Place a socket over the end of the grease nipple so that it rests on the nut
  5. Gently bash on socket


When reassembling the brake, note that:

Rear Wheel Brake Pedal, Brake Rod

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Brake Pedal Wear

Over time, a Triumph rear brake pedal pivot becomes a loose fit. This would be an easy fix if Triumph had used a bushing there, but they didn't. Here's how one listee fixed the problem:

WWW icon WOL: Sloppy Brake Pedal


Brake rod cotter pin

With everything assembled, it's nearly impossible to splay the cotter pin that fastens the rear brake rod to the brake pedal lever: therefore, do it at one of these stages of disassembly:

Rear Wheel Fender Bracket

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Parts icon Fig.26 Fenders


Bracket fits inside the rear frame loop. See TBA photo.

Rear fender bracket on frame 1/2" bolts (same bolt used for oil bottle bracket).

Rear Wheel Fender


Parts icon Fig.26 Fenders
WWW icon ""Fender Drill Pattern Templates", Good tips on fitting a new rear fender


  1. Nut from bolt that fixed front of fender
  2. Nuts from bolts through fender bracket at shocks
  3. Nuts that clamp fender to frame loop
  4. Tail light


Note that the two rear fender bracket mounting bolts (14-0113) Parts icon(Ref 32 Figure 26) must be installed before putting on the fender.

Rear Chain

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WWW icon  Drive chain lubrication Opinions on chain lubrication - take your pick
WWW icon  New rear chain Long thread on chain specs/brands with an emphasis on Renold chains
WWW icon Final drive chain Regular vs sealed (o-ring) chain and more Renold comments

Removing Chain

When working with the rear chain a short section of plastic rain gutter beneath keeps the chain and the floor clean.

Replacing Chain

Checking Chain for Wear


WWW icon ""Measuring Chain Wear", Greg Burns

As Burns points out in his article "Measuring Chain Wear" (link just above), chains don't stretch, they become longer due to the pins wearing an oblong pattern in the bushes.

When wear reaches the point where the chain is no longer a perfect match with sprocket teeth, wear to both sprockets is accelerated greatly.

There are differing opinions as to how much wear is acceptable before replacement is necessary - compare the workshop manual's guidance with that offered in the Burns article.

The workshop manual says to check wear this way:

That works out to 1-1/4" of wear on 100 links.

Burns, on the other hand, states that "Most chain manufacturers limit chain wear to approximately .006" per link." That works out to .6" wear per 100 links.

Which is right? I'm inclined towards the more stringent standard suggested by Burns for the simple reason that a new chain costs less than two sprockets and is a lot easier to change!

Cleaning Chain

For asphalt riding I clean and lubricate every 1,000 miles when I change crankcase oil/filter and primary chaincase oil. When I'm mostly riding the gravel I drop down to 500 mile intervals. Works out to just over a half-dozen cleanings per season on average.

The used kerosene in the second container can be recycled many times. Within a few days the suspended sediment will have settled to the bottom and the clear kerosene on top can be gently poured off for the next cleaning.

Lubricating Chain

After cleaning

Using a pot or pan, immerse clean chain in heavy (summer) chain saw bar oil overnight. Hang to drip-dry the next day and then wipe lightly with a clean rag before reinstalling.

Pull the clean chain back on with the old chain.

After riding

Upon returning from rides, apply bar oil to warm chain with the tip of a gear oil container through the chain inspection hole in the chainguard. But take care not to apply an excess of oil because it will find it's way into the rear wheel brake drum.

A great way to contain oil dripping off the chain is to place a short piece of old roof gutter below it. Excess oil drips are easily wiped off the gutter with a rag.


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Manual icon Dunlop Tire Tips and Technical Specifications (PDF).
WWW icon "Best tyres for nervous handling 1969 TR6C...." (tires & tire pressure)
WWW icon "Tyres!!" (tire preference thread)

Tire Pressure

Modern versions of vintage tires are constructed of far better materials than the originals and the workshop manual's 18/20lbs air pressure spec is far too low.

The first several years I had Bonnie I used the WS manual's recommendation and always found that my front tires were cupping. Going to 30/32 pounds front and back eliminated the cupping.

Front Tire and Tube

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Dunlop K-70, 3.25 x 19

Rear Tire

Dunlop K-70, 4.00 x 18

Tubes for Dunlops

Put valve stem to yellow dot.

Frame - Stands - Tin - Pegs

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Icon for manual Workshop Manual (1969 650cc Twins) Section E: Frame and Attachments (TOC)

Swinging Arm


Icon for manual Workshop Manual (1969 650cc Twins) Section E8: Removing and Replacing the Swinging Fork
Icon for manual Workshop Manual (1969 650cc Twins) Section E9: Renewing the Swinging Fork Bushes
Parts iconFig.13 Swinging Arm, Rear Shocks


When replacing the swinging arm, the large 15/16" nut (Ref 10) and tab washer (Ref 9) go on the DS, and the 7/8" bolt (Ref 8) head goes on the TS.


Was getting a bit of back-and-forth play (grab two loose ends and try to rotate swinging arm left or right) so I replaced the pivot bushes (ref 2) in 2014 (53,010 miles).


Don't be tempted to put the shocks on before the swinging arm because they'll just be in the way.

Like the first time, I had difficulties getting the bolt to thread into the frame on the drive side. But now I know the trick - after trying to push the swing arm this way and that way in an effort to get the threads to take I finally got the idea to use the impact screwdriver with a 9/16 BS or 7/8" socket. Tapped the driver with my plastic mallet while turning slowly and the bolt went right in no sweat!


Assembled 2 sleeve bushes (5/36) and spacer (6/36) with flanged washers and new o-rings, packing with grease as they went

Inserted the bolt, using a small diameter dowel to help line up the spacer and bushes.

Put the nut on loosely and used grease gun to fill until grease bled out both ends. Note\; I wouldn't put much pressure behind the grease because excess will have to be squeezed out the holes when the swing arm is inserted into the frame brackets.

Used plastic mallet (lightly) to position the arm and inserted the bolt. Likewise, played with other end a bit with the mallet and the bolt threaded into the frame bracket on the primary side.

I initially torqued the bolt (8/36) - 7/8" socket - to 50 pounds (the new torque wrench is fun!) but the swing arm was binding slightly so I backed off a tiny bit until it was free.

Use 15/16" socket for the nut (10/36).


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Parts iconFig.12 Side stand


Easier to remove with stand folded against frame. Use 3/4" wrench to remove nut (faces out) and then give the bolt a rap to loosen up and start on its way out. Then open the stand and wiggle while pulling on the bolt. Slip the spring off after the bolt is removed.


Nut is up and out or it will be in the way of the spring.

Easiest way to get it on is to put the spring in place on the frame and the sidestand and then pull the sidestand into place.

Center Stand

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Parts iconFig.12 Center stand
WWW icon "Center stand spring"
WWW icon "Installing a center stand spring"
WWW icon "Bonneville center stand" (twisting)
WWW icon "Install Center Stand Spring Using String"
WWW icon Table: Triumph 650 Center Stands & Mounting Hardware

Replacing Center Stand Spring

If the stand is off the bike the spring can be levered on using the stand.

If the stand is on the bike, see "Install Center Stand Spring Using String"

Left/Right passenger footrest brackets

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Parts icon Fig.29 Passenger Footrest


Remove left-hand bracket to make it easier to access the bolt holding the chainguard "C" clamp to the torque stay.

Brackets need to be slack to insert bolt for rear footpegs from behind - best to pre-assemble.

Rear Frame

The 23/34 bolt on the bottom is 5/8" used 1/2" socket.

The 21/34 bolt head is also 5/8", but its 21/34 nut is 11/16", spanner for the former and 1/2"socket for the latter.

Powder Coating

Bonnie's frame and tinware Photo icon have been powder coated, as well as the following parts:

Not powder coated:

Battery Carrier

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Parts iconFig.24 Battery Carrier
Parts iconFig.23 Oil tank
Photo icon Battery Carrier/Oil Tank Mounting (2 photos)
Photo icon Battery Carrier (8 photos)

Reinstalling Battery Carrier and Oil Tank

There may be better ones, but this order of assembly works ok

  1. Insert rubber spigots (82-6673) into oil tank
  2. Place rubber grommet (82-6039) and lower oil tank mount bracket (82-6147) into the loop for the bottom oil tank mount
  3. With bottom of oil tank raised towards you, offer it to the frame, rotating it down into place with a sideways wiggle to make the froth tower clear the mounting bracket on the frame.
  4. Insert screwed peg 82-7510 from left to right for left hand tank mount
    Lubricate with Murphys soap or WD-40 and tap it in with a plastic-faced mallet or squeeze it in with water pump pliers (protecting finished surfaces with a few layers of rag)
  5. Insert screwed peg 82-7510 from right to left for right hand tank mount
    Lubricate with Murphys soap or WD-40 and tap or squeeze it in To get enough of a swing, the strap can be pulled up
  6. Put on plain washers (60-4248) and nuts (82-0879)

    Regarding the next 4 steps: it's much easier to put the rubber spigots (82-6673) inside the battery holder straps and then push them onto the frame lugs then it is to put the spigots on the lugs and push the carrier straps over them.

  7. Insert rubber spigot (82-6673) into the long (rear) battery holder strap (82-8028)
  8. Lubricate the spigot and push it and the rear battery holder strap onto the rear frame lug
  9. Insert rubber spigot (82-6673) into the short (front) battery holder strap (82-9255)
  10. Lubricate and push onto the front frame lug
  11. Connect the oil tank to the batter holder straps with bolt (14-0103), rubber washer (82-6968), plain washer (60-4248), and locking nut (14-0701).
  12. Adjust oil tank for clearances and low stress and tighten fasteners

See also: Oil Tank


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Parts iconFig.25 Seat, side panel

To remove seat, first remove left side panel, then remove bolts for just one seat hinge and slip the other one off.

Installing seat latch: push latch part way through it's frame, insert spring and washer, then the rest of the way through. Keep spring and washer in place with right-angle pick while inserting cotter pin.

The Electrical System

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Icon for manual Workshop Manual (1969 650cc Twins) Section H: Electrical System (TOC)
WWW icon MagnetoMan: "Rewiring a Motorcycle"
WWW icon RF Whatley: "Electrical System Grounding"

Trouble-Shooting Electrical Problems

WWW icon ""Fault-Finding Flow-Chart for Motorcycle Charging Systems"

Short Circuit

If your bike is blowing fuses, this trouble-shooting tip from John Healy will be a great help in tracking down the short: replace the fuse with a 12v light bulb and then begin disconnecting circuits one at a time. When the light goes out you're found the circuit which is shorted. Start looking for faults such as worn insulation or loose bare wires.

Lucas Wiring Color Codes

Lucas electrical wiring color code chart

Bonnie Electrical System 2015 (no dip switch, no horn)

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Triumph 650 with Pazon electronic ignition wiring diagram (with no dip switch)

Bonnie Electrical System 2015 (with dip switch and horn)

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Triumph 650 with Pazon electronic ignition wiring diagram (with dip switch)

Bonnie Electrical System Schematic 2006

Custom wiring diagram for Triumph 650 motorcycle with Pazon electronic ignition upgrade

Original Electrical System Schematic

Wiring diagram for 1969 T120R 650 Bonneville (export market)


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Parts iconFig.23 Battery Carrier/Oil Tank
Photo icon Battery Carrier/Oil Tank Mounting (2 photos)
Photo icon Battery Carrier (8 photos)
WWW icon " Motobatt (Triumph 650 search)"

Battery Specs

Replacement battery should be a sealed, maintenance-free unit with a minimum 9Ah rating. Carrier inside dimensions: H x W x D.

Possible replacements:

Brand/Part# Height Width Depth Notes
Koyo YTX-12-BS 5-1/8" 5-7/8" 3-5/16" 5 stars, but hard to find
Motobat AGM MB9U 13.6cm 13.3cm 7.6cm 12v/11aH $65US on Amazon
PowerStar PM9A-BS AGM 5-1/2" 5-1/4" 3.0" 12v/9aH $49.95US at LowBrow
PowerStar AGM PS-12-BS 5-1/8" 5-7/8" 3-3/8"  
Yasua 5-1/8" 5-7/8" 3-3/8" (June 2018)


Use 35 amp British fuse, or 15-17.5 amp US fuse (continuous slow-blow).

When I rewired with my homemade harness I fused both the positive and negative battery terminals. Effectively this is like having a spare fuse at all times.

While on a trip to the Green Mountains in 2015, I blew a fuse in the middle of nowhere when I turned on the ignition key while coasting down a steep hill in fourth gear. Bang! A big pop and the ignition was dead. No spare fuses with me - they got left at home on the workbench! I recovered by shorting together the fuse carrier leads for positive and putting the good fuse in the negative lead.

Battery Carrier

Jump to Battery Carrier section.


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WWW icon John Healy "Lucas Electrical Stator or Rotor Install Guidance" (PDF)
WWW Stator Installation

Stator Studs

If stator holes won't line up with the stator studs in the crankcase, or the rotor is off-center in the stator, do not be tempted to adjust the alignment by hammering on the studs. Doing so risks cracking the crankcase, best to do any bending with the studs removed and held in a bench vise. (See stator link above).

Rotor Integrity


Icon for manualTriumph Service Bulletin "Loose rotor center or rotor retaining nut"

The way the Lucas rotor is constructed, it's possible for the rotor center to become loose from the outer part holding the magnets. This can be checked by tightening the rotor in place with the stator removed. Gripping the rotor with both hands, turn over the engine in both directions and feel whether there is any slipping movement. Rotors that have become loose cannot be repaired ordinarily, they must be replaced.

Rotor and Stator Clearance

See note above on Tightening Rotor Nut.

When reinstalling the rotor, important to be sure there is sufficient clearance (.008"-.012") all the way around between it and the stator.

Here's a method often cited at the Britbike Forum:

Checking Alternator for Charging

With engine running and lights on, blip the throttle. If intensity of headlight does not increase with revs there is a problem somewhere in the charging system. This can also be verified by connecting a voltmeter across the battery terminals to see if voltage rises when revs do.

The alternator can be checked by connecting either a voltmeter (AC) or a 12 volt bulb across the alternator's disconnected leads and kicking over the engine.

Wiring Harness

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Photo icon Original Wiring Harness - 2005
Photo icon New Repro Wiring Harness - 2006

Removing Stock Main Wiring Harness

The selenium rectifier and grounding straps have already been disconnected.

  1. Pull apart bullet connectors to tail light
  2. Free tail light switch
  3. Clamp from spring to brake rod has 5/16", or better, 1/8W nut and slotted bolt head
  4. Disconnect wires (bullets) to contact breakers
  5. Disconnect ignition switch and remove
  6. Remove zenner diode and bracket
  7. If installed, remove bullet connectors to front brake light switch
  8. Remove head light bolts
  9. Pull harness forwards, through fork and out

Routing of Wiring Harnesses

(See original and repro photo sets above)

Main harness

Beneath gas tank. Tied about an inch to the rear from the "Y" (along with clutch cable) to upper tube through space in frame forward of the coils. Then tied again to upper tube just forward of the rear gas tank mount. Passes over the top of the rear loop into the battery area. Photo icon (Photo)

Horn/Dimmer harness (gray plastic)

Passes through the stanchions from the rear Photo icon (Photo)

2006: Eliminated horn and integrated dip switch wiring into the Lucas lighting switch in the headlight shell (see wiring diagram above)

Rear brake switch harness

2006: Tied just above bottom side cover mounting stud and then falls to follows the frame member before looping to the switch.

Notes on 2006 Wiring Harness Replacement

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Headlight and Headlight Shell

Photo showing Bonnie's headlight shell wiring:

Photo of Triumph headlight shell wiring

Headlight Reflector/Lense Fixing Clips

The headlight reflector unit (99-0686, or LUCAS 516798) is held in the headlight rim (99-0692, or LUCAS 553248) using fixing wires (99-683, or LUCAS 504665).

WWW icon Classic British Spares: "Installing & Removing Lucas Headlight Wire Clips"

Triumph 650 Lucas headlight and rim photo showing mounting clip orientation

LED/Halogen Headlight Bulb Replacement


WWW icon Head/Tail/Brake Light LED Replacements
WWW icon thread Brett: "LED headlight bulb test: Now with Pictures!"


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Parts iconFigure 35 Ign coils, Horn, Rectifier, Zener diode
WWW icon Twin horn relay wiring 1970 T120R

Lucas 35710 Light Switch

I've replaced this switch three times on Bonnie. After installing new repro switches I've attempted to recondition the old ones by taking them apart and re-assembling. Never had any success, maybe you're more lucky than me.

The figure below shows the internal connections of the Lucas 35710 (99-0563) light switch in all three positions. See also this chart-style pin-out for the 35710.

Diagram of Lucas 35710 Lighting Switch showing internal electrical connections

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Photo of Triumph ignition switch

Ignition switch

Repro editions of the Triumph ignition switch are notoriously prone to failure and the slightest weight of a key fob attached to the key is known to exacerbate the problem - leave your ignition key naked!

An intermittent ignition issue is frequently due to a defective ignition switch. If you're having an ignition problem, one of the first things to do is install a jumper lead from the battery to the coils, thus by-passing the ignition switch.


Selenium Rectifier

Note: Selenium rectifier replaced by Podtronics Rectifier/Voltage Regulator in 2015


Photo of Triumph 650 selenium rectifier showing wiring connections Schematic diagram of Triumph 650 selenium rectifier wiring connections


Condensers eliminated by Pazon in 2014 (left wiring in place and all original condenser parts, brackets, covers, etc. are retained in inventory.

Had previously (2006, new harness) fabricated a custom bracket and moved condensers from original location to beneath gas tank. See photo below.

Often suspected that Bonnie's habit of firing on only one cylinder after encounters with water (car washes, rain storms) might originate here. Especially when the problem persisted after waterproofing the ignition wires' passageway through the timing case to the points.

Ignition coils


Parts iconFigure 35 Ign coils, Horn, Rectifier, Zener diode

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Triumph ignition coil and custom condenser mounting

Installing Ignition Coils

Note that the head steadies must be installed before installing the ignition coils.

Testing Ignition Coils

Note that just because correct resistance readings are obtained for a coil does not mean that the coil is good. It may be arcing internally or its readings may change when the coil becomes warm.

Resistance readings for 6v coils:

Resistance readings for 12v coils:

Ignition Coil Wiring Connections

With Pazon

Left Coil (DS)

Right Coil (TS) Schematic diagram for Triumph 12v ignition coil wiring connections

With Repro Harness (2006)

Left coil

Right coil

With Original Harness

Photo Photo icon

Left coil

Right coil

Ignition Coils Replacements

2017: Replaced 6v TriCor coils with 6v Taiwanese units (76,000mi).

2014: Replaced 12v German ignition coils with 6v TriCor 'High Spark' coils during changeover to Pazon CDI.

20??: Replaced 12v Lucas coils with 12v German units during changeover to Pazon CDI.

(12v originals & German coils are in inventory, along with one good 6v TriCor.

Pazon Ignition

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Pazon PDF Installation, timing, and trouble-shooting

Pazon Schematic Diagram

Wiring schematic for Pazon electronic ignition

Pazon - Trouble-Shooting

WWW icon Nick, posting on
  1. "With the ignition on check you have 12 volts or so between the red and white wires on the Pazon and 12 volts or so between the coil supply and the white Pazon wire.
  2. "Place a voltmeter between the Pazon black wire and the white wire, when you switch the ignition on the reading should be about 1 volt or so for a few/ maybe 10 seconds then it should go to 12 volts. (this is the unit switching the coils off under 'stall conditions' to prevent the coil burning out) It will cause a spark at the plugs if the coils are ok.
  3. "If that doesn't work the black box unit is faulty or has been damaged.
  4. "If it worked then connect one side of the sensor with the ignition on and momentarily touch the other sensor lead to it's connector, this should also create a spark at the plugs. If it doesn't, check the resistance across the sensor connections, it should be between 120-250 ohms from memory but sometimes vibration can break the track or the fine sensor winding connections on that plate.

"This will tell you if the box or the sensor is the problem."

Boyer Ignition Trouble-Shooting


WWW icon "How to Trouble-shoot a Boyer Ignition" Includes good info relating to all EI systems

Podtronics Rectifier/Voltage Regulator

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manual icon Podtronics: Instructions & Diagram
WWW icon Podtronics Home Page
Photo icon Rectifier/Voltage Regulator Installing beneath battery carrier


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First run (2 miles - Chemin Vallieres)

Second run (5 miles - Ayers Cliff)

Third run (28 miles - Tyson's Corner)

Fourth run (50 miles - Sherbrooke)

Fifth run (50 miles - Katevale,Magog,Gendron,GVille,Brown's Hill, Ayers Cliff)


High revving problem was due to such poor condition of o-ring for idle adjustment that the idle screw had no friction and just kept screwing itself in (higher revs) each time i adjusted it. A new o-ring fixed the problem right up.

Although cable friction was not to blame for high-revving, i nevertheless decided to eliminate the cable tie I'd put around upper member beneath gas tank to hold throttle cables as well as clutch cable tight to the frame. Without the tie they take a larger radius arc and seem more "relaxed".

Severe miss and dead battery due to

I corrected above and timed the engine first using Hancox's static method and then using the strobe. Running really well!


About The Bonnie Ref

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"The Bonnie Ref" is an outgrowth of my efforts, as an amateur, to maintain and repair "Bonnie", my 1969 T120R Triumph Bonneville. From the very beginning I have been the beneficiary of much help and information from fellow CVMG club members, the BritIron mailing list, and classic Triumph forums such as and

To organize the information and make it accessible, I used HTML and hyperlinks. Tired of the dark, blurry photos in workshop and repair manuals, I included my own digital photos and illustrations created in Fireworks 2.0 (I own it, it's mine - screw Adobe!). Eventually I began linking to useful information from around the Internet.

I am not a mechanic or expert by any means, but I hope you'll agree that this "manual" provides quick and easy access to volumes of interesting and useful information on the late 60's Triumph 650 motorcycles. Enjoy!

Corrections, suggestions, or comments welcome: tmc at

Cheers! and Happy Trails
Bruce Miller (The Hermit)

About Bonnie

1969 Triumph Bonneville T120R

The Triumph Meriden factory began production for new model years in August of the prior year. In October 1968, during the 1969 model year, Triumph changed to a new serial number system. The new serial numbers used two letters to designate the month and year of production, and a 5-digit serial number, beginning at either 00100 or 00101, depending upon what source you read. So, in October of 1968, Bonnie was either the 24th or 25th Triumph twin to use the new serial number system.

I purchased Bonnie from Frank Holmes at Frank's Brit-Barn in New Hampshire on June 28, 2003. There were just over 14,000 miles on the clock. She came in very original condition and complete except for Windtone horns.

I re-styled Bonnie to look more like the 1966 models I had 'back in the day'. Things like fitting '66 retro tank badges, stainless steel fenders, and steering damper, moving the zenner diode from the headlight back to the side panel, and dispensing with the exhaust pipe balance tube. All of the original parts - tank badges, fenders, seat, exhaust & mufflers, handlebars, carburetors, points, and many others, I've kept, so possible to restore to near-original condition.


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adhesive/sealant products
adjust primary chain tension
adjust valve rocker clearance
air cleaners, installing
air filters
air screw o-ring
air slide (carb)
align rear wheel
alpha-Numeric part# conversion
alternator, checking
Amal parts, '69 650s
annealing head gasket
anti-seize compound
applying heat
axle retainers, rings, and dust covers
axle parts, front illustrated
axle parts, rear illustrated
Banjo bolts, orientation
battery carrier, reassembling
battery specs & replacements
Boyer Ignition trouble-shooting
brake light, switch
brake light, switch harness routing
Brake, front
brake, front - adjusting
brake, front - centering shoes
brake, front - reassembly
brake, front - removing
brake, front - replacing
brake pedal, D.S. engine mount, torque stay
brake pedal wear
Brake, rear
brake, rear - centering shoes
brake, rear - disassembly
brake, rear - reassembly
brake shoe illustrations
brake torque stay
British standard threads
cables, lubricating
cables, routing
cable, speedometer
cable, speedometer - lubrication
cable, tach
cable, tach - lubrication
cables, throttle
camshaft, degreeing-in
carburettor cables,air slide,spring
carburettor choke
carburettor, cleaning idle jet
carburettor, concentric cross-section
carburettor, flooding
carburettor, jet/needle/cut away
carburettor, leaking float bowl
carburettor, mid '69 BSA modification
carburettor O-rings
carburettors, specs & settings
carburettors, synchronizing
carburettors, removing as a unit
carburettors, trouble-shooting
Carburettors, tuning
  Amal tuning links
  high speed
  low speed & sync
Center stand
center stand spring
center stands/mounting hardware
chainguard, replacing
Chain, rear
chain, remove
chain, replace
chain, checking wear
chain, cleaning
chain, lubricating
clutch assembly, removing
clutch assembly, replacing
clutch cable
clutch center/thrust washer compatibility
clutch operating mechanism "pops"
clutch pressure plate adjustment
clutch rod adjustment
compression testing
compression, sudden loss of
connecting rods
contact breaker points gap
crankcase breather pipe
crankcase oil, changing
"crush", head and PRTs
cylinder base bolts, removing
cylinder block & tappet blocks
cylinder block, honing and replacing
cylinder block, painting
cylinder block, removing old gasket
Cylinder Head
cylinder head bolts, leaking
cylinder head bolts, re-torquing
cylinder head bolts, torquing
cylinder head, cleaning
cylinder head "crush" and PRTs
cylinder head, removing old gasket
detonation, pre-ignition
distance pieces, rear axle
Electrical system wiring diagrams
Electrical wiring color codes
electrical, Pazon ignition schematic
electrical, misc.
electrical, Podtronics schematic & instructions
engine compression
engine, installing
engine mounting plate fasteners
engine, removing
engine sprocket, align w duplex sprocket
exhaust pipes
float and float needle
footpegs and brackets, passenger
Front Fork
front fork, alignment
front fork, dismantling
front fork gaiters
front fork oil
front fork, remove as unit
front fork, remove legs separately
front fork seals, replacing
front wheel bearings
front wheel brake
front wheel brake shoes, illustrated
front wheel fender brackets/stays
fuel lines
fuel lines, plastic and safety
fuel lines, removing carbs with
fuel lines, removing connectors from gas taps
gaiters, front fork
gaskets, removing old
Gas tank
gas tank, paint schemes
gas tank sealers/liners (link)
Gas taps, removing & replacing
Gas taps, sealing
gear cluster, installing into gearbox
gears, illustrated
gearbox problems - resources
gearbox assembly: three methods
gearbox illustration
gearbox, indexing camplate & quadrant
gearbox inner cover
gearbox inner cover, removing
gearbox inner cover, replacing
gearbox, jumping out of gear
gearbox, outer cover
gearbox outer cover, removing
gearbox outer cover, replacing
gearbox oil change
gearbox oil compatibility
gearbox, power transmission illustrated
gearbox, removing bearings from casing
gearbox, replacing bearings in casing
gearbox, replacing inner cover bearings
gearbox, sealing inner/outer covers
gearbox sprocket
gearbox tear-down notes
gear shifter
General Data T120/TR6
General Shop Info
grease gun, mini
Handlebar grips
handlebars, shock absorber mounting
handlebars, removing bonded bushes
Head bolts, see Cylinder head bolts
head gasket, annealing & installing
headlight bulbs, breaking
headlight bulb LED/Halogen replacements headlight reflector/lense fixing wires
headlight shell wiring diagram
heating cases & other parts
heat insulation, carbs
horn/dimmer switch harness routing
idle screw o-ring
ignition coils, installing
ignition coils, replaced (Bonnie)
ignition coils, testing
ignition coil wiring connections
ignition switch connections
Ignition Timing
indexing gearbox camplate & quadrant
Issues, history of
kickstart lever tapered pin
layshaft end play, measuring
layshaft thrust washer locating pegs
Loctite products, stick form
Loctite, where to use (John Healy)
Lucas wiring color codes
Lubrication Schedule
main jet
mainshaft bearing, replacing in inner cover
mainshaft/layshaft bearings, removing
mainshaft/layshaft bearings, replacing
manuals, download
needle jet
needle jet pin gages
O-Ring Sizing Chart
o-rings, carb to intake manifold
o-rings, dimensions for prt seals
o-rings, front fork dust excluder sleeve
o-rings, idle & air screws
o-ring & insulation block carb mounting
o-rings, push rod tubes
o-rings, swinging arm
o-rings, rocker arm spindles
o-rings, tach gear housing
oil, zinc content
oil breather line
oil, changing crankcase
oil filter
oil leaks, drain bolts
oil lines
oil pump
oil pressure switch
oil pressure relief valve
oil seal, D.S. crankshaft
Oil tank
oil tank, reinstalling
paint schemes
parts lists, factory
parts lists, proprietary
Pazon Sure-Fire PDF
Pazon, schematic diagram
Pazon, setting timing with
Pazon, trouble-shooting
pilot air screw
pilot jet
pin gage for needle jet
pistons, removing
pistons, replacing
piston rings, gapping
piston rings, installing
piston rings, orientation
Points Ignition
points, contact breaker gap
powder coating
pre-ignition, detonation
pressure plate, adjusting
Primary Chaincase
Primary chaincase gasket
primary chain adjustment
primary chain wear (photos)
primary chaincase oil, changing
pushrods & rocker boxes, replacing
Pushrod Tubes (PRT)
pushrod tube o-rings
pushrod tube seals
pushrod tube o-ring & seal dimensions
pushrod tube seal "crush"
pushrod tube installation
Rings, gapping
Rings, installing
Rings, orientation
Rear frame
rear wheel
rear wheel alignment
rear wheel bearings
rear wheel brakes
rear wheel brake shoes, illustration
rear wheel brake shoes, centering
rear wheel fender
rear wheel fender brackets
rear wheel, removing
rear wheel, replacing
removing old gaskets
re-torquing head bolts
rings, gapping
rings, installing
rings, piston
rocker arm spindles
rocker arm spindle o-rings
Rocker Boxes
rocker box gaskets
rocker box gaskets, lightweight pr mod
rocker boxes, remove
rocker boxes, replace
rocker clearance, adjusting
roller bearing conversion for steering neck
rotor, loose center
rotor installation guide
rotor nut, torqueing
rotor to stator clearance
sealant products
selenium rectifier connections
serial numbers, 1950-1969
serial numbers, 1969-1983
service bulletins
shock absorbers, rear
shocks, disassembling/installing
side panel
slide (carb)
spark plugs
Speedometer and Tachometer
speedometer cable
speedometer gearbox
speedometer gearbox lube
sprocket, gearbox - replacing
stanchion tubes, replacing
stator installation guide
stator studs
stator to rotor clearance
steering damper
steering head
steering lock
Swinging arm
switch, Lucas 35710 - wiring diagram
switch, ignition
switch, brake light (rear)
tach cable, lubrication
tach drive gearbox, removing
tach drive gear, lubrication
Tappet guide blocks
Thackary spring washers
timing cover, removing (link)
timing, see Ignition timing
tires, Dunlop technical reference (PDF)
tire, front
tire, rear
tools, special
torque settings, head bolts
torque stays, engine
trouble-shooting, carburation
trouble-shooting, electrical
upgrades (
valve clearance, adjusting
valves, replace in head
wiring, Lucas color codes
Wiring diagrams, electrical system
wiring diagram, headlight shell
wiring harness, horn and dimmer switch
wiring harness, rear brake switch
wiring harness, removing (stock)
wiring harness, replacement in 2006
wiring harness, removing
wiring harness, routing
Workshop manuals, factory
zinc, in motor oil