The Bonnie Ref

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

Most Recent Online Update: December 8, 2018

Manual/Tech Bulletin Parts Illustration Special Tool Photograph World Wide Web YouTube Video


adhesive/sealer products
adjust primary chain tension
air cleaners, installing
air filters
air screw o-ring
air slide (carb)
align rear wheel
alpha-Numeric part# conversion
alternator, checking
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
camshafts, degreeing-in
carburetor cables,air slide,spring
carburetor choke
carburetors, cleaning idle jets
carburetors, concentric cross-section
carburetors, flooding
carburetors, high speed tuning
carburetors, jet/needle/cut away
carburetors, low speed tuning & sync
carburetors, mid-range tuning
carburetors, mid '69 BSA modification
carburetors, specs & settings
carburetors, synchronizing
carburetors, removing as a unit
carburetors, troubleshooting
Center stand
center stand spring
center stands/mounting hardware
chainguard, replacing
Chain, rear
chain, remove
chain, replace
chain, check for stretch
chain, cleaning
chain, lubricating
clutch assembly, removing
clutch assembly, replacing
clutch cable
clutch center/thrust washer compatibility
clutch operating mechanism "pops"
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, removing old gasket
Cylinder Head
cylinder head, cleaning
cylinder head "crush" and PRTs
cylinder head, removing old gasket
cylinder head bolts, leaking
cylinder head bolts, re-torquing
cylinder head bolts, torquing
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 Forks
front forks, alignment
front forks, dismantling
front forks oil
front forks, remove as unit
front forks, remove legs separately
front forks 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
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, 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 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
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
needle jet
needle jet pin gages
o-rings, idle & air screws
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, troubleshooting
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
pressure plate, adjusting
Primary Chaincase
primary chain adjustment
primary chain wear (photos)
primary chaincase oil, changing
pushrods & rockerboxes, 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
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
roller bearing conversion for steering neck
rotor installation guide
rotor nut, torqueing
selenium rectifier connections
serial numbers, 1950-1969
serial numbers, 1969-1983
service bulletins
shock absorbers, rear
shocks, disassembling/installing
side panel
slide (carb)
Speedometer and Tachometer
speedometer cable
speedometer gearbox
speedometer gearbox lube
sprocket, gearbox - replacing
stanchion tubes, replacing
stator installation guide
steering damper
steering head
steering lock
switch, lighting - 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
torque stays, engine
upgrades (link to thread
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

Hermit's Proprietary Lists

Hyperlinked Illustrated Parts Lists

Torque Settings

Special Tools

Other Lists

Links, Articles & Features

Hermit's Classic British MC Links

Hermit's 650 Tech Articles

Bonnie's Back Pages


Parts Sources


Workshop Manuals

Downloads/Other Manuals

Factory Parts Lists

Vintage Fastener Specs

Triumph Service Bulletins

Additional Info

General Shop Info


  • BA - British Association (see Threads, below)
  • BSF - British Standard Fine (see Threads, below)
  • BSC - British Standard Cycle(see Threads, below)
  • BSW - British Standard Whitworth (see Threads, below)
  • CEI - Cycle Engineering Institute - same as British Standard Cycle (BSC)
  • D.S. - Drive Side
  • O.A. - Overall Length
  • L.S. - Left Side (D.S.)
  • L.H. - Left-Hand thread
  • MES - Miniature Edison Socket (Bulb 3W-MES bulb 643)
  • PRT - Pushrod Tube
  • R.S. - Right Side (T.S.)
  • TP - Thread Profile
  • TPI - Threads Per Inch (see Threads, below)
  • T.S. - Timing Side
  • TSB - Triumph Service Bulletin
  • U.H. - Under Head
  • UNC - Unified National Coarse (see Threads, below)
  • UNF - Unified National Fine (see Threads, below)
  • UNEF - Unified National Extra Fine (see Threads, below)

Alpha-Numeric Part Number Conversion



 baconsdozen, Ebay 
Understanding Whitworth BSF AF BA & metric tools

SAE threads


  • Unified National Fine
  • Same as American National Fine
  • 60 degree thread angle
  • Unified bolts may/may not have a circular depression on the bolt head, or three interlocked rings on one of the flats


  • Unified Coarse
  • Same as American National Coarse
  • 60 degree thread angle
  • Unified bolts may/may not have a circular depression on the bolt head, or three interlocked rings on one of the flats

British Standard threads


  • British Association
  • Diameters less than 1/4 inch
  • Prefix number (e.g. 12BA) indicates size (lower number=larger)


  • British Standard Cycle/Cycle Engineers Institute/Cycle
  • Three names for the same thread
  • 60 degree thread angle
  • Used mostly in steel fasteners


  • British Standard Fine
  • British automotive industry
  • Finer than UNC, coarser than UNF and BSC
  • 55 degree thread angle
  • Used mostly in aluminum/alloy castings


  • British Standard Whitworth
  • Coarse thread used in aluminum
  • Compatible (same tpi) w American coarse (60 degrees) from 1/4" to 7/16"
  • 55 degree thread angle

English wrenches are stamped with the diameter of the bolt, while American wrenches are stamped with measurement across the flats.

Some charts (like one abovet) list 1/2" and up as 26 TPI, while others list 1/2" and up as 20 TPI, and still others list both 20 and 26 TPI.

Adhesive/Sealer Products John Healy: Where to use Loctite on a Triumph Kadutz: Loctite products in stick format
  • Hylomar (Newman Tools)
  • Loctite blue thread locker
  • Loctite thread sealant
  • Loctite anti-seize Lubricant - head bolts, sparkplugs
  • Permatiex Ultra-Black gasket
  • Right Stuff gasket (sealing chaincase exit of alternator wires)
  • Wirth caulking (? untried)

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 sealer on the splines for the engine and gearbox sprockets? Too late this year (2018).

Applying Heat "Heating Engine Cases & Other Parts"

Whether it be for removing bearings from cases or loosening up seized-up parts, some heat can help out enormously. The question is, how much heat? And how to apply it? Find some clues in the link just above.

Mini Grease Gun

Loading instructions.


Crankcase Oil
Percentage of Zinc Content for Popular Oils Very informative synthetic oil thread
540ratblog "Motor Oil Engineering Test Data" "Crankcase vent tube discharge question" TR7RVMan elucidates upon Triumph crankcase venting "Tech 101: Zinc in oil and its effects on older engines"

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 convertors. 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.

Oil-change at 1,000 mile intervals.

  • Capacity: 6 Imp pints - 7 1/4 US pints - 3 Liters
  • Oil tank filter nut is 1" wrench (remove once a year)
  • I progressively lean bike over on center stand and front wheel while the hot oil drains from the oil tank.
  • Drain bolt beneath crankcase -13/64" is perhaps tighter than 1/2BS (7/16W).

Oil Filter

Colorado Norton Works
Oil Filter Adaptor for Norton Filter Head

In 2011, at 43,000 miles, I fitted Bonnie with a Norton oil filter head, as diagrammed above.

The mounting bracket was milled by Robert St-Cyr, guided by Glenn "Phrog" Davidson's design, as brought to you by GABMA.

The oil tank connections and the oil pipe junction block pipes are all 1/4" OD. The connections on 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 1,000 mi.

I religiously change crankcase oil, oil filter, and primary chaincase oil at 1,000 mile intervals.

Filters for use With standard Norton filter head

Filters I used with the Norton filter head satisfactorily include:

  • Norton 06-3371 (/E, /G, /ER) ($9-16.00Cdn)
  • Wix 57013 (CarQuest, Magog $15.02Cdn) (Amazon, $11.55US)
  • HD 63810-80A/63782-80
  • Fram PH6019 (Amazon, $10.70-$14.53US)

Although the following filters are said to be the same size and have the same thread and general characteristics as the Norton filter, most of them are not easy to find.
  • Crosland 631 or 673 (No listing found)
  • Mann W7 12/70 (No listing found)
  • Jones Filtration 264
  • Fram PH2839 (No listing found)
  • Simca 29932 M
  • Unipart GFE 212
  • AC 5 W
  • NAPA 1352, made by Crosland (No listing found)
  • CarQuest 85352 (white in colour) (No listing found)
  • Champion H101 (No listing found)
  • Wipac CA101 (No listing found)
  • Delco X5 (No listing found)
  • TJ FB2094

In May 2017 I purchased an oil filter adaptor from Colorado Norton Works. The adaptor permits use of filters which are easier to find and less expensive, list follows:

Filters to use with the Norton filter head & Colorado Norton Works adaptor

  • CarQuest 85348 (CarQuest, $8.44Cdn)
  • Wix 51348 (Amazon, 12/$57.70US) )
  • Fram PH3614 (Amazon, $4.26US or 2/$16.99US)
  • Purolator 10241 (Amazon, $8.80-11.80US)
  • NAPA 1348 (Amazon, $8.99US or 12/$73US)
  • AC Delco PF53 (Amazon, $4.47US)

Primary Chaincase Lube

  • Change at 1,000 mile intervals with crankcase oil
  • 350cc 30w non-detergent oil

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.

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

Gearbox Lube "The Effects of EP Additives on Gearboxes"
Lucas oil representative 'Don't use our products with yellow metal' (2014) "Bronze-friendly gear oil recommendation?" Hermit's In-progress gearbox oil/yellow metal experiment
  • Change annually or at 5,000 mile interval
  • 500cc of 90W GL-4 gearlube

Gear Oil Compatibility

There are conflicting opinions about the suitability of various kinds of gear oil for Bonny gearboxes with their bronze thrust washers and bushings.

Oils with the following characteristics have been tagged by some as being unfriendly to bronze. On the other hand, many express the opinion that such cautions are unwarranted with modern gear oils. Some flatly claim that any gear oil is ok.

Thought to be yellow metal unfriendly in many, but not all quarters:

  • EP (extreme pressure) oils
  • Hypoid oils
  • Oils with limited slip additives
  • Oils with high sulphur content
  • Oils with the GL-5 or GL4/GL5 additive packages

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.

So, here in 2018 I've ordered from online:

  • Red Line (50304) MT-90 75W-90 GL-4 Manual Transmission and Transaxle Lubricant - 1 Quart
  • "Less slippery low sulfur formula compatible with brass synchronizers"

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.

It is not necessary to remove the index plunger and its holder to drain the oil. The plunger holds the camplate in place, so if you do decide to remove it, take care not to move the camplate or it may become necessary to re-index the camplate and quadrant.

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

Ideas on preventing oil leaks from crankcase, primary chaincase, and gearbox drain bolts "
How to stop oil and gear box drain plug leaks?".

Front Forks

  • Change fork oil annually
  • Use 200cc of 10w fork oil

Draining Fork Oil
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

  • Grease fitting on gearbox annually

Swinging Arm Bushing

  • Grease swinging arm fitting annually

The Oil Tank

Fig.23 Oil tank
Battery Carrier/Oil Tank Mounting (2 photos) A thread with some interesting info on oil tanks, oil pumps, and oil flow A thread on repairing Triumph oil tanks Another oil tank repair thread 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 waterpump 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.

The Engine

Fig.2 Crankcase
Fig.14 Engine Mounting Plates, Footrests
Triumph Overhaul Manual, Unit 650s '63-'67 TR7RVMan's advice on preparing for a complete engine teardown Torque wrench settings ->Rods ->Tappets & Cams

Engine Removal and Installation

Engine Removal
Removing engine using chain hoist Removing engine using floor jack & muscle

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 up on 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: 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. 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


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

Fig.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:

  • Gently lock vicegrips onto hose and twist and push and pull
  • With hose in left palm, twist and pull while pushing the hose with fingers of right hand.
  • Place spread tips of locked needlenose vicegrips against the ends of hoses and push using the pliers handle and thumb and fingers of other hand. Be careful not to scrape oil tubes.

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)

Warning! Correct installation of oil lines is crucial.
Reversed connections result in inadequate lubrication and engine failure.

On Bonnie (NC00125) without an oil filter:

  • The rear oil tank connection goes to the forward oil junction block connection
  • The forward oil tank connection goes to the rear oil junction block connection

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

Feed Oil Line

  • The rear oil line connection (union nut) on the oil tank is the feed line
  • The feed line goes to the forward connection pipe on the oil junction block (Haynes, p.38)

Return Oil Line

  • The forward oil line connectin on the oil tank is the return line
  • The return line goes to the rear connection pipe on the oil junction block

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.

Crankcase Breather

Fig.2 Crankcase
Fig.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

 Fig.3 Oil Pump
  Oil Pump

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

  • 1963 - 1966: E3878 (Scavenge 0.437"/ Feed 0.374")
  • 1967 - Early 1969: E6928 (Scavenge enlarged to 0.487"/ Feed 0.374")
  • Late 1969 - 1979: E9421/ 70-9421 (Scavenge 0.487"/ Feed enlarged to 0.406")
  • 1980 and on: 71-7317 'double check-valve' pump (same 0.487"/ 0.406").

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

Oil Pressure Relief Valve

Fig.3 Pressure Relief Valve

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

Oil Pressure Switch

Fig.6 Timing Cover
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

Fig.5 Cylinder Block
Fig.3 Tappet Guide Blocks

Replacing Tappet Guide Blocks
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 tappts would ride up and down freely. Only did this after buying another exhaust guide block, so I have a spare.

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. "Re: L F Harris Pistons/Rings" (honing cylinders) "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.

  • Dave helped me install the barrels over new rings the first time. Even with four hands it was not easy!
  • The second time (after replacing the tappet guide blocks) I used ring compressors and it was much easier.
  • In 2014 Paul helped me and we just fiddled around until the barrels dropped on.
  • In 2016, again with Paul's help, I went back to using the ring compressors and they worked very well. I tightened the compressors right down until the rings were closed. Then, with the pistons blocked up with wooden rails, we slipped the cylinder block on. The weight of the block easily overcomes the resistance offered by the tightness of the compressors on the rings.

Tightening 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.

Connecting Rods

Fig.1 Connecting Rods
Triumph Service Bulletin #317 "Self-locking nuts on big ends" (as shown in #7).


Fig.1 Pistons Removing Pistons

Removing Pistons

To remove grudgeon pins, heat pistons to around 100C. In 2006 I used way too much heat, so in 2016 I monitered the temperature using the digital laser thermometer. Also in 2016, I first packed snow in plastic bags around the pistons to chill the grudgeon 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 grudgeon pins and, if necessary, heat the pistons. In 2016 I only chilled the grudgeon 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.

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! -


Fig.1 Rings
Triumph Service Bulletin "Piston Ring Replacement"
Triumph 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

Fig.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.

Annealling 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 headgasket. Burrs, it's said, can become hot spots and cause pre-detonition (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 rockerbox 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 cleaner.

Installing Cylinder Head & PRTs

Installing Pushrod Tubes & Cylinder head below.

Torquing Cylinder Head Bolts

Put new head bolts on Bonnie in 2016.

Torque Settings

  • Head bolt #1- 15 pounds - ?
  • Head bolts #2-9 - 18 pounds - 5/16W
  • Rocker box 1/4" bolts - 5 pounds - 3/16W socket
  • Rocker box nuts - 5 pounds - 3/16W or 7/16" box end

Torque figures given are for dry threads. One recommendation is reduce by 20% when wet. On Bonnie this would mean using 15lbs instead of 18, but I confess I do 18 (but not more) even when using anti-seize compound.

Hancox's method is to start with #1 and take them all right down to the end torque. I did that in 2006 and it worked ok, but I feel more confident doing an incremental 'round robin'. That is, tighten bolts 2-9 to 10 pounds, then to 15, and finally to 18 pounds.

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

In 9-8-7-6-5-4-3-2-1 order, back off head bolts by one flat one at a time and re-torque to specs. And always remember to re-adjust valve tappet clearances after re-torquing head bolts.

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 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

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

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

Because the Thackary spring washers could become fowled 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:

  • Rockerbox
  • Flat 3/8" thrust washer
  • Thackary spring washer
  • Rocker
  • Flat 1/2" thrust washer
  • Rockerbox center
  • Flat 1/2" thrust washer
  • Rocker
  • Thackary spring washer
  • Flat 1/2" thrust washer
  • Rockerbox

The updated layout (NOT used by Bonnie):

  • Rockerbox
  • Thackary spring washer
  • Flat 1/2" thrust washer
  • Rocker
  • Flat 1/2" thrust washer
  • Rockerbox center
  • Flat 1/2" thrust washer
  • rocker
  • Flat 1/2" thrust washer
  • Thackary spring washer
  • Rockerbox

Rocker Arm Spindle O-Rings

Ed Holin
"What is the correct O ring for the rocker spindles on a '71 Triumph T100R and similar bikes?".
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 - 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:

  • (2) 3/8" head bolts and plain washers (5/16W).
  • (3) stud nuts with flat washers (7/16" box-end)
  • (2) 1/4" rocker box bolts and flat washers (7/16 box-end)


Pushrod Tubes (PRT)

Fig.5 Pushrod Tubes

PRT O-Rings

Triumph Service Bulletin #18-69
"PRT O-rings leaking oil - 1969 'B' & 'C' Range"

The table below shows push tube o-rings used between 1969 and 1971. In 1971 the red, high-temperature 71-1283 o-ring was introduced for use on top. Red ones I installed seemed to quickly crumble.

Later, 71-1283 became available in Viton, and that is definitively the way to go. Bonnie uses Viton 71-1283 o-rings top and bottom and, generally speaking, leakage is not a problem.

  #7 '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

PRT Seals

Triumph Service Bulletin 324
"Sealing the pushrod tubes"

Note that two PRT designs were used between 1968 and 1973 on "B" range 650 machines: 70-9349 ("fabricated"), and 71-2575 ("one piece"). My Bonnie (1969 model year built in Oct 68) has the one-piece part.

Bonnie has been upgraded for PRT seals as shown in the '71 USA parts book and Triumph Service Bulletin 324 Pushrod Tube Oil Seals

The upgrade uses a square-sectioned sealing ring retained by a metal band, the so-called 'wedding band', to seal between the bottoms of the pushrod tubes and the tops of the tappet blocks.

The square-sectioned sealing rings are commonly silicon and available in different thicknesses for adjusting 'crush' (see 'crush' below).

Getting Proper Amount of "Crush" on PRT seals

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

When the head is sitting freely (loose bolts) on top of the cylinders and pushrod tubes with seals and gaskets in place, there should be between .030" and .040" gap - called the 'crush' - between the cylinder head and the head gasket.

Too much crush results in a poor seal and oil leaks, too little risks distorting the head when head bolts are torqued down.

The crush is adjusted by substituting different thicknesses of sealing rings. A thicker sealing ring holds the PRTs and the head higher and increases the crush. A thinner seal decreases 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 tighly 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 ballpeen) 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

The following dimensions could help in adjusting for proper sealing ring crush.

Head 2.755"
2.785 (Internet forum)
Head Gasket .045-.050
Round O-rings 70-7310 (Buna-n)
71-1283 (Viton)
.987" I.D.(Nom 1") - .103" thick
Square-sectioned sealing rings 71-1190 0.033 (Rabers' spec)
70-3547 0.093" (3/32") (.091 Rabers' spec)
70-4752 0.125" (1/8") (.123 Rabers' spec)
70-1496 0.1875" (3/16") (.177 Rabers' spec)
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

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.

Replacing Push Rods and 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 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 rockerbox 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 rockerbox.
  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 rockerboxes, give a few squirts of oil to moving parts.
  6. Introduce the rockerbox from the middle, and, looking up from below, manuevre it into place without touching the pushrods. When the three studs are lined up on their holes, gently let the rockerbox 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 rockerbox, 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 rockerbox 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), rockerbox bolts (21-1875, UNC 1/4-20TPI X 2 5/32 U.H. Tool-3/16W Torque: 5 LBS), and rockerbox 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.

Replacing Engine Torque Stays

Fig.14 Engine Torque Stays Engine Torque Stay Fasteners. StuartMac on assembling the engine torque stays


Fig.5 Valves
 Vintage Bike Magazine John Healy: "Where is your valve seat?"
 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

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.

Adjusting Valve/Tappet Clearance

I tend to err slightly towards extra clearance because it is better to have a bit too much than not quite enough. Too little clearance and the valve may not fully close (and therefore burn) when the engine is hot. Too much leads to 'hammering'.

Sound is an important guide while setting clearance (see 'clicks' below) and when evaluating results, engine running.

Far easier to adjust valves before reinstalling carburetors when they were previously removed. Otherwise, just remove gas tank and air filters.

Coarse adjustment by position

Run adjustors in until they contact the valve stems and then back them off: ~1/8 turn for exhaust , and ~1/16 turn (half of 1/8) for intake.

Fine adjusting by feel

  • .004" - Easy to feel movement and hear somewhat sharp clicking
  • .002" - Can just feel the movement (half of .004") and gentle, muffled clicking is just audible

A two-piece tappet adjuster tool makes it a little easier to control the stock square-headed adjusters, but ultimately I found that allen head adjusters work best. An allen key and a box-end wrench on the locking nuts has

Positioning Valves for Clearance Adjustment

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

  • To adjust DS exhaust tappet (tappet in up position, valve closed), open the TS exhaust valve by positioning the tappet all the way down.
  • To adjust TS exhaust tappet (tappet in up position, valve closed), open the DS exhaust valve by positioning the tappet all the way down.
  • Likewise for the intake tappets.


  • To adjust DS exhaust tappet (tappet in up position, valve closed), open the DS intake valve by positioning the tappet all the way down.
  • To adjust TS exhaust tappet (tappet in up position, valve closed), open the TS intake valve by positioning the tappet all the way down.
  • Likewise for the intake tappets.

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 tappet 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

    Safety Alert
    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:

  • Best to coordinate movement of allen key and wrench to 'drift' towards a new clearance setting rather than loosen the lock nut and try to hold the allen key at the desired position while tightening the nut

  • When loosening and tightening the lock nut and while 'drifting' towards new setting, make all movements in 'slow motion' to obtain the most accuracy

  • The lock nuts don't have to (shouldn't) be torqued down very hard - should be able to loosen them with a smart thump on the wrench handle with a couple of fingers

Adjustment after Retorqueing

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 retorqueing the headbolts

Engine Compression

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:

  • Warm up the engine
  • Replace spark plugs one at a time with compression tester
  • Hold the throttle wide open
  • Give five or six smart kicks to the kickstarter
  • Read tester for compression

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

  • If compression improves significantly the cylinder isn't sealing properly: suspect rings/cylinder bore. 

  • If compression doesn't improve, suspect leaking valves/valve guides.

If valves are suspected, check to ensure no tappets are too tight, preventing valves from closing fully.

Sudden Loss of Compression "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 Left   120
Three heat cycles after top-end job 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 na 135
  Right na 145-50
2010 / 43,500mi Left 145 150
  Right 120 150
2006 / (Frank's) Left 165-170 na
  Right 165-170 na
2006 / 28,600mi (fresh after top-end rebuild) Left 135 na
  Right 135 na

Timing Chest

Fig.6 Timing Cover "Removing timing cover"

Cam Timing
"How to Degree In Your Camshaft" (PDF)

Ignition timing
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 Hermit's Illustrated Ignition Timing with Points TR7RVMan: Ignition Timing w. Points

Contact Breaker Points Gap: .014-.015-.016"

Setting Ignition Timing with Pazon

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.

  • Use the Clockwise timing hole in the Pazon circuit board
  • Rotate circuit board until the red dot is under the Clockwise timing hole

Dynamic Timing

Use strobe on either cylinder for dynamic timing

  • Rotating the Pazon plate clockwise causes the strobed timing mark to move counterclockwise (retards timing)

  • Rotating the Pazon plate counterclockwise causes the strobed timing mark to move clockwise (advances timing)

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

Triumph Service Bulletin #12-68 "Spark Plug Cross Reference Chart" Trouble-shooting Dry & Wet Fouling of Spark Plugs How to Read Your Spark Plugs

Used NGK for quite a while, but have returned to using Champion NC3 (801).

Plug gap: .025".

Interpretting 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

Fig.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.

  • The nuts on the exhaust pipe clamps are 7/16"
  • The nuts on the Phillps head screws holding the exhaust pipes to the chrome brackets are 7/16"
  • The nuts and bolds holding the muffler hanger strap to the muffler brackes are 1/2"
  • The nuts holding the chrome exhaust brackets to the engine are 5/16" BS (removal unnecessary to pull exhaust pipes)

When removing or replacing the exhaust pipes over the exhaust pipe adaptors (spiggots), 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

Clutch, figure and part listing
Primary Chaincase, figure and part listing
 YouTube Raber's Tech Tips, Episode #4 - Triumph Unit Construction Twins Cush Rubber Installation 'Unit 650 clutch thrust washer' Clutch thrust washer discussion, inc. types & changes in size. TR7RVman's clutch tips Restoring & maintaining the Triumph clutch.

Primary Chaincase

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

Adjusting Primary Chain Tension

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 Primary chain tension adjuster D2108 into the drain hole.
  3. Hold engine against compression with kickstart lever (Service 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.

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

Dismantling the Transmission

The clutch assembly, engine sprocket, and primary chain are removed simultaneously after removing the stator and rotor.
Fig 10 (Clutch) and Fig 11 (Primary Chaincase).


  1. Drain chaincase oil and slacken primary chain Primary chain tension adjuster D2108
  2. Slack off the left side footpeg (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 Wheel Puller
  9. (Store rotor AWAY from metal/magnets)
  10. Loosen engine sprocket ( 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 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 clutch locking tool & a 7/8 socket and breaker bar.
    If difficult to remove, use air wrench
  16. Loosen clutch center from mainshaft ( 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 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:

  • thick washer on DS crankshaft in front of engine sprocket
  • Thrust washer - some 'rings' evident

Things that were kind of loose:

  • Rotor nut - not very tight - (reinstalled with Blue Loc-tite)
  • Rotor stud - finger loose - (reinstalled with Blue Loc-tite torqued to 35lb)
  • Clutch nut - came off fairly easily - (torqued to 50+lb)

Notes on Removing the Clutch Center


In 2016 I began carefully tightenting 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 sheared off length-wise. I also noted that the clutch hub had spun on the mainshaft.

Clutch Center & Thrust Washer Compatibility John Healy: Thrust washer/clutch center compatibility 'Unit 650 clutch thrust washer' Thrust washers, discussion of types & changes to size 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:

  • Copper-clad steel both sides (these may be the best)
  • Copper-clad on one side, steel on the other (the steel side to the hub may wear more quickly than copper-clad)
  • Solid bronze (these apparently wear the fastest and may be attacked by some lubricants)


  • Some solid bronze washers are chamfered on one side of the inside diameter
  • Original copper/steel washers and some solid bronze washers have tabs to prevent the washer from turning

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

Reassembling the Transmission

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
    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
  11. Install distance piece over crankshaft, chamfer towards sprocket
  12. Install 71-0082 woodruff key and rotor
  13. Install 70-3975 tab washer and 70-3977 shouldered rotor nut
  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

  • Sprocket Alignment After installing the duplex sprocket, the engine sprocket, and the primary chain, be sure to check that the engine sprocket and the duplex sprocket are aligned to each other. This can be done with a steel straight edge. placed across the engine sprocket boss to see if it aligns with the duplex sprocket boss.

    If the sprockets are not aligned, use shims (70-8038 .010", 70-8039 .015", 71-2660 .030") between the engine sprocket and the crankshaft bearing to align them.

  • The clutch nut was about the only nut I didn't use loc-tite on in 2016. I used Blue on the kickstarter rachet nut, inner and outer cover fasteners, the rotor nut, the trap door screws, and the oil junction block nut (from which I also removed the previously installed loc washer and replaced with the proper flat washer).

  • Trap door - in 2016, renewed countersunk screws holding on the trap door. I noticed last year that one of the screw hole's threads were stripped. It's the one at 12 o'clock. I slathered it with blue loc-tite and tightened it down as much as I dared.

  • When replacing the D.S. crankshaft oil seal, the springs face the sprocket according to the WSMan.
    Some say this is an error (Triumphrat vintage forum) and that it should be the other way around because the pressure is from the crank side. Others say WSMan is correct because it would be worse to contaminate engine oil with clutch oil than the other way around. Think I'll stay with the WS Manual.

  • When replacing stator, note that the three nuts holding it on should be torqued to 20lb

Adjusting the Pressure Plate

Triumphrat Forum
Peg's clutch 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 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?).

Clutch Rod Mechanism pops or clicks

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

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 this problem, do this:

  1. Back off cable adjusters until clutch cable is completely slack and the clutch lever (57-2191) inside the outer gearbox cover is at rest
  2. Adjust the clutch rod adjustment pin (57-2159) by turning it out 1/2 turn from contact between it and the clutch rod (57-1736) (not 1 turn as per WS manual)
  3. Re-adjust clutch cable adjusters
  4. Important to leave some slack at the hand lever end of the clutch cable. I think 1/8" would be minimum, I leave Bonnie's quite slack.

The Gearbox

Fig.9 Gearbox outer cover  /  Fig.7 Gearbox inner cover  /  Fig.8 Gearbox, gears and shafts
Triumph Service Bulletin #329 "Third gear ratio and selector forks modifications" Index to other Hermit Gearbox Articles Clearances & Specs for Selected Gearbox Components John Healy: Indexing 4- & 5-speed gearboxes (leaf-spring and plungers) Kevin Roberts: Profusely illustrated post on upgrading 5-speed gearbox Engine Base for pressing in gearbox DS needle bearing

Shifting and Power Transmission: Stills & Animations 
Stills, Rear View Gear Animation, Rear View (wait for it) Stills, Front View Gearshift lever & gear shift quadrant deflection from center Gear Animation, Front View (wait for it)

Gearbox Lubrication

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 and in 2008.

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 about two miles up the road.

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 gearchange quadrant.

When I finally replaced the gearchange quadrant in June of 2016, it fixed the problem straight away. The old gearchange 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 gearchange quadrant installed in the outer cover, I fitted a degree wheel to it to observe how far the gearchange 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.

Gearbox Problem Resources

Triumph Service Bulletin #329 "Third gear ratio and selector forks modifications"
Triumph Service Bulletin #8-59 "1969 650s jumping out of 2nd/3rd gears"
Triumph Service Bulletin Troubleshooting excerpt: "Improper Upshift, Third Gear" "Gear selection malfunctions after gearbox overhaul" The thread I started on Bonnie's shifting problem "69 Bonneville jumping out of gear" "T120 unit gearbox problem" "Gear Lever movement" Faulty gear selection thread John Healy: 4/5-speed gearbox conversion Inc. photos comparing 4- & 5-speed components
YouTube Lunmad: Gearbox Video

Outer Gearbox Cover

Fig.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.

Kickstart Lever Tapered Pin

If removed, be sure to replace the tapered pin from the rear with the kickstart lever in the upright position. That is, the nut should face forward or it 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 gearchange quadrant"

Replacing Outer Gearbox Cover
Posidrive screw locations in outer geabox 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

Fig.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
    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 (1 11/16" socket)

Inspecting the Gearbox Components

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 guage end play.

  • Place soft lead solder or Plastiguage (TM) inside of closed end and assemble as usual. After bolting on inner cover, disassemble and measure thickness of solder. Subtract .003-.005" and insert suitable shim behind thrust washer.

  • Assemble and bolt on inner cover. Grasp end of layshaft with pliers, presumably using a protective covering. Move the shaft in and out to measure end play with a dial guage. Reassemble using suitable shim.

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)

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

Replacing Gearbox Inner Cover Bearings

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

The gearbox casing holds two bearings:

  • Layshaft bearing (57-1606 needle roller 1 1/6" x 7/8" x 3/4")
  • Mainshaft bearing (57-0448 ball journal 1 1/4" x 2 1/2" x 5/8")

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: 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 indespensible trick was to use the old mainshaft as a "stick" to line up the large mainshaft bearing (57-0448) squarly with it's housing in the gearbox casing ( Photo). Once it was started squarly I used a large, heavy drift against the outer race to drive home the bearing ( 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
Side-by-Side Comparisons of Three Methods: WSManual, Hughie Hancox, & Haynes Hughie Hancox Method: Step-by-Step with Photos

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

Whatever method you use, keep in mind that on many models, including the '69 T120, the hole for the the shifter forks shaft is drilled right through the case and, if left un-sealed, may become a source for leaking gearbox oil. I've used Permatex Black and Hylomar with good results. Others recommend Loctite.

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 copule 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

Method 1: Juggling

  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
  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
  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

Method 2: Juggling

  1. Hold layshaft thrustwasher 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 screwdrive 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

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 acheived 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

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

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 a new hole for a replacement peg. "Locating peg repair"

Indexing the Camplate & Quadrant "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:

  • When indexing with the camplate in 1st gear position, the quadrant is raised from the down position to mesh with teeth on camplate
  • When indexing with the camplate in 4th gear position, the quadrant is dropped from the up position to mesh with teeth on camplate
  • When indexing with the camplate between 2nd and 3rd gears, the quadrant is held 'level' to mesh with teeth on camplate

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

Replacing the Inner Cover

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 "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

Gas tank

Fig.22 Gas tank "Bruce Hamilton: "FAQ: Automotive Gasoline" (inc. bibliography) "Best Tank Sealer" "Triumph paint thread" R Moulding's excellent paint thread, illustrations and discussion "Triumph Bonneville Paint Schemes 1959-1970" John Healy via Rask Cycle "Stepless Ear Gas Line Clamps"

When replacing the gas tank, I tighten the rear mount fastener first, and then the two front ones. If the nuts in front are tightened first, it "springs" the rear of the tank upwards.

The threads in Bonnie's frame for the rear tank mount are stripped. At least one of my other two unit 650s had this problem also. A large tie-wrap over the tank's rear mounting tab (bolt and all rubber parts in place) and through the sidecar mounting hole works well, but as per above, tighten the tie-wrap before tightening the nuts on the studs in front.

Bonnie's TS front tank mounting stud came loose once. Leon Goldick, Montreal, gave Bonnie her magnificent paint, and he made the repair and touch-up.

Gas Line

I've always used the clear, reinforced, stock-type fuel lines on Bonnie along with crimped ferrules.

The problem is the plastic becomes hard fairly quickly and it becomes more difficult to keep it leak free. Tygon LP1100, a low permeation EPA and CARB certified fuel line, is said to remain soft longer, but all plastic hardens with time and UV exposure.

After reading all the way through this TriumphRat 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 carburetors 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


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

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.


Fig.31 Concentric 930
Triumph Service Bulletin #2/73 "Checking & Adjusting the Amal Concentric Float" John Healy: "Amal Concentric Carburetters" (2017) John Healy: "Tuning Your Carburetter" (2013) Jim Bush: "Bushman's Carb Tuning Secrets" "Bonnie carb jetting help needed" (reading spark plugs w. illustrations) "Amal manuals for Monobloc & Concentric (inc. Premier) carbs" Jeffery Diamond: "Super-Tuning Amal Concentric" (Advertisement for booklet) "Notes on Rebuilding the Mark-1 Concentric Carburetter" Richard Whatley: "Leaking Amal Carburetters" "Amal Concentrics, How they Work and Tuning" "Motor dies just as I take up throttle cable slack" Electrical or Carb? Informative thread "Pin gauges for needle jets" Long, informative thread on needle jets
 YouTube Raber's Tech Tips, Episode 6: Triumph 1971 T120 Bonneville Amal Carb O-ring Installation


Amal Concentric 930 Cross-Section

Amal Concentric Carburetor Parts

Summary of Carb Specs & Settings

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 richer2 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 matchups are:

 Needles Needle JetJet 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). 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:

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

OTH, 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.

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."

Adjusting Low Speed Mixture & Idle Speed & Synchronizing Carburetters

The Workshop manual explains how to sync carburetors 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 Carburetters (no Low-speed adjustment)

  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

Note: The next two sections use the term "8-stroking". John Healy offers this description of 8-stroking on

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, thats lean at the needle jet or needle position, try lifting the needle one notch..."

High Speed Tuning

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.

Carbutettor - Reading the Signs

Loud banging from exhaust with no throttle and engine braking is a classic symptom of a an exhaust pipe leak at the head. Triton Thrasher on

Softer 'popping' in the exhaust is an indication of running lean, either as a result of an out of adjustment air-screw adjustment or air leaking in between the intake manifold and the carburettor. Triton Thrasher on

If the air screw must be adjusted more than 1 1/2 turns out, it could mean that the air slide cutaway is too rich. John Healy 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, thats lean at the needle jet or needle position, try lifting the needle one notch..." Gavin Eisler on

At full throttle, if the motor picks up a little when rolling off the throttle, the main jet is too lean. Gavin Eisler on

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 forword edge of the oil tank.

  • Important. When threading the air cleaner adapters onto the carburetors be extremely careful to avoid cross-threading. The adapters are steel and the carburetors are very soft pot metal. Grasp adapters lightly on either side with finger tips and as lightly as possible thread them on. They should pretty much spin on with NO resistance. If there is any significant friction the adaptor is probably cross-threaded. Remove gently and try again.

  • When properly positioned, a) the holes in the air cleaner's chrome cover face down and the solid part faces up, and b) the securing screw and clip are on the inside where they are concealed.

    Here's a way to get everything aligned properly:
  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 carburetor 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 carburetor

Air Filters

  • Paper
  • Wire gauze

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

Fig.28, Cables Mike Partridge: Control Cable Tips
Tri-Cor Cables, England Cable Chart

Lubricating Cables

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 forks 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 carburetor 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 carburetors now have two nipples between the cables and the carburetors.


Throttle cables originally "crossed over", i.e. the outboard cable on the twistgrip went to the D.S. carburetor.

Throttle Twist Grip

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

  • The screw on the bottom is the friction screw.
  • The screw on the top is the throttle stop - it stops the throttle grip when the slides are all the way up so excessive tension is not placed on the throttle cables.

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

Speedo and Tachometer

Fig.33 Speedo and Tach


  • Rebuilt by Nissonger 20??@??Kmi
  • Rebuilt by Andy Henderson 2014@60Kmi

Disassebly & 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.

  • O-ring for tach gear housing plug (70-6300, Ref.# 22)
  • O-ring for tach driven gear housing bushing (70-6299, Ref.# 25)
  • O-ring for tach driven gear housing (70-3309, Ref.# 27)

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, execess grease will be expelled at cable connection to drive unit.


  • Speedo died at 75Kmi. but odometer still works
  • Rebuilt by Andy Henderson 2014@60Kmi
  • Exchange unit (Nissonger, from Frank Holmes) 2006@31.5Kmi

Speedo Cable

  • Speedo cable nut at gearbox end is 9/16"
  • Three ties - 1) down tube, 2) beneath main frame, and (3) swinging arm frame.

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-lubed as I could just barely detect a light coat of grease. I emailed Andy and he replied that his cables are indeed pre-lubed 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 speedo gearbox and speedo head.

Speedo Gearbox

Grease periodically - small greasegun.

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


Fig.18 Handlebar mounting, steering damper  /  Fig.27 Handlebars, control levers, steering damper (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 eyebolts and if they are not present the eyebolts can be stressed to the point of breaking. (John Healy).

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

Note If the eyebolt makes contact with the the head lug, see
Triumph Service Bulletin #306
"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 hairspray. I tried hairspray once and quickly learned how dangerous that idea is. Hairspray 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?


Rear Shock Absorbers

Fig.13 Swing arm, rear shocks "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 forks and Steering Head

 Fig.17 Front Forks  Front Fork Components
 YouTube Raber's Tech Tips, Episode #2 - Triumph 500 / 650 Front Axle Widths
 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 forks 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

Steering Damper

Fig.18 Steering Damper Steering Damper Fitment by Years 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.

Removing Front Forks 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 forks... they're 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 forks - 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 ( 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 Forks

  1. Remove cork washer and gaiter
  2. Remove spring abutment and spring
  3. Remove dust excluder sleeve with 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 restrictors 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 forks seals: May 2014/March 2007/May 2003.

  • Replace lower plain washer BEFORE putting new "o-ring" into dust excluder sleeve
  • Built up ends of PVC damping sleeves go DOWN
  • Open side of oil seal goes DOWN
  • Fitting oil seals:
    To prevent damage to edge of seal, place plastic wrap or plastic bag over end of stanchion tube and slide the seal either all the way down on greased plastic film, or on a plastic sled over the greased stanchion tube.

    Slide seal down stanchion, place stanchion in lower fork leg and use it to position seal while pressing seal into place

  • Ends of gaiters with pin holes go DOWN
  • Don't forget to replace fork covers (headlight mounts) before inserting stanchion tubes through lower and upper yokes!

Refitting Stanchion Tubes

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

Refitting Forks to Frame

With front forks 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 Forks

When replacing front wheel and axle, the front forks 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 forks as much as possible
  4. Tighten the axle cap bolts on the side where they are finger tight

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

Refitting Without Forks

(For refitting with forks, see Refitting Forks 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

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.

Front Axle Parts Illustrated
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.

Rear Axle Parts Illustrated
This photo shows the orientation of all parts on the rear axle, including axle nuts, chain adjusters, spacers, grease retainers, retaining ring, backing ring, and speedometer gearbox.

Front Wheel

Fig.19 Front Wheel Replacing Rims - Devon vs Central Wheel Bearing Locking Ring Wrench

Front Wheel Bearings
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 Front Brake Shoe Illustrated Stuart provides many details on various Triumph hub, anchor plate, & axle setups

[Replaced Bonnie's front shoes May 2014 @60kmi]

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 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

  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

Front Wheel Fender Brackets/Stays
StuartMac: Tips on fitting the front fender stays to forks

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 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

Fig.20 Rear Wheel Replacing Rims - Devon vs Central Tidbits about chain guards

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 chain
  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

Fig.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 needlenose 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

When reinstalling the rear wheel the speedometer gearbox must be positioned so that the speedometer cable lines up straight with the swingarm 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 rather a trial-and-error proposition.

  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

In order to prevent the rear brakes from 'pulsing', the brake shoes should be centered to the axle. This is done by applying the brakes while tightening the inner axle nuts.

The inner axle nuts can be tightened with the wheel in place but that requires a very thin 3/4" wrench. I don't have a suitable wrench, so I center the brake shoes and tighten the nuts on the workbench. With the tire held in a bench vise, I use a two-foot piece of pipe with one end squashed to hold down the brake actuating arm while tightening the inner nuts.

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. It is much easier to fit the nut and bolt with the passenger peg and mounting plate removed.

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

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

Rear Wheel Brakes

Rear Brake Shoes Illustrated


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

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:

Replaced May 2014 60,000 miles

With wheel in bench vise, used squashed 2" pipe to apply hard rear brakes while tightening inner hub nuts with socket and crescent wrench.

At first I made it just a bit tight and the gearbox for speedo wanted to turn with the hub. Tighter, still turned. Really tight and the gearbox stayed tight, but wheel was binding.

Wheel still turning (very) stiffly at start of test ride, but easier after 2 miles. After another 5 test ride miles the wheel was turning very freely with no binding.

Rear braking is quite improved and no longer pulses as it did for the past two years.

Rear Wheel Brake Pedal, Brake Rod

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: 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

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

Fig.26 Fenders


  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) (Ref 32 Figure 26) must be installed before putting on the fender.

Rear Chain  Drive chain lubrication  New rear chain Final drive chain

Removing Chain

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

  • Position master link on the rear sprocket
  • Use ballpeen and small drift or screwdriver to dislodge the master link clip and then push out the master link
  • Use the master link to connect the working chain with an old chain and use it to pull off the chain you're removing
  • Leave the old chain in place for when you're ready to replace the working chain

Replacing Chain

  • If the chain was removed with an old chain, just hook the chains together with a master link and pull the replacement chain on
  • If the chain was removed completely, feed chain from front to rear over top of rear sprocket through the spokes using a chopstick from the T.S. with pointed end inserted in hole of last link
  • Replace master link with chain ends on the sprocket

    Sometimes, especially with a new chain, it's difficult to get the master link into the two ends of the chain on the backside. If so, put an old master link in from the front, then go around to the backside and push in the new master link, displacing the other one as you go.

    Always orient the open end of the clip down with the master link positioned at the rear of the sprocket. Another way to think of it is to picture the clip as a fish and install it so that it is climbing up the rear sprocket as if it were spawning.

  • Chain adjuster bolts take a 1/2" wrench

Checking Chain for Stretch

Place chain on a flat surface and line links up in a straight line with a straight edge. With the links compressed together there should be 12 1/2" between pivot holes twenty links apart. With the links stretched out there should be a maximum of 12 3/4" between the holes. So 1/4" stretch over 20 links, max.

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.

  • Use an old chain to pull the chain off and then back on after it's been cleaned
  • Place rolled-up chain in an old 4-quart pot
  • Just barely cover the chain in kerosene
  • Swirl around and around in the pot
  • Gently pour off the kerosene into a second container, leaving the sediment behind in the cleaning container
  • Wipe the sediment from the cleaning vessel with a rag
  • Repeat until kerosene is clean and no more sediment comes out of the chain (usually around six rinses)
  • With each rinse, less kerosene can be used

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) chainsaw 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.


Dunlop Tire Tips and Technical Specifications (PDF). "Best tyres for nervous handling 1969 TR6C...." (tires & tire pressure) "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

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

Swinging Arm

Fig.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).


Fig.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

Fig.12 Center stand "Center stand spring" "Installing a center stand spring" "Bonneville center stand" (twisting) "Install Center Stand Spring Using String" 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

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 have been powdercoated, as well as the following parts:

  • Cylinder block
  • Lower triple tree
  • Front fork lower legs
  • Battery carrier
  • Muffler hanger brackets
  • Chain guard (new English repro)

Not powdercoated:

  • Side panel
  • Oil tank
  • Front fork spring abutments

Battery Carrier

Fig.24 Battery Carrier
Fig.23 Oil tank Battery Carrier/Oil Tank Mounting (2 photos) 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 spiggots 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 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


Fig.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 MagnetoMan: "Rewiring a Motorcycle" RF Whatley: "Electrical System Grounding" ""Fault-Finding Flow-Chart for Motorcycle Charging Systems"

Lucas Wiring Color Codes

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

Larger Image

Bonnie Electrical System 2015 (with dip switch and horn)

Larger Image

Bonnie Electrical System Schematic 2006

Original Electrical System Schematic


Fig.23 Battery Carrier/Oil Tank Battery Carrier/Oil Tank Mounting (2 photos) Battery Carrier (8 photos) " 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 slowblow).

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

See Battery Carrier here.


John Healy
"Lucas Electical Stator or Rotor Install Guidance" (PDF)

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.

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. One method mentioned at the Britbike Forum is to

  • Cut four to six pieces from a coke can (.004") that are about one inch longer than twice the width of the rotor
  • Fold them over double to make .008"
  • Off the bike, place the rotor inside the stator with the shims between them
  • Offer the rotor/stator/shim assembly to the stator studs
  • If necessary, use the assembly to push against the studs and adjust their position until the entire assembly slides easily all the way on
  • Install nuts and washers and tighten
  • Using pliers, grab the protruding shims and pull them out - they should slide out freely if clearance is good all the way around

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
Original Wiring Harness - 2005 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 forks 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.

Horn/Dimmer harness (gray plastic)

Passes through the stanchions from the rear

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

  • British Wiring ~$159
  • Eliminated front brake light (tied down)
  • Eliminated oil pressure switch (cut lead)
  • Re-wired light switch for high/low beam
  • Relocated zenner diode to side panel
  • Turn signal wires not included in loom (really?)
  • Snipped off lead (orange/green?) in headlamp shell was for oil pressure switch
  • Double brown/white lead loose in headlamp shell was for zenner diode beneath headlamp
  • Double brown/blue lead loose near condensers under tank is for the horn
  • Yellow/black ignition wires go to TS ignition coil
  • White/black ignition wires go to DS ignition coil

Headlight Shell Wiring

Headlight Reflecter/Lense Fixing Clips
Classic British Spares: "Installing & Removing Lucas Headlight Wire Clips"

The headlight reflector unit (99-0686, or LUCAS 516798) is held in the headlight rim (99-0692, or LUCAS 553248) using fixing wires (99-0683, or LUCAS 504665).

LED/Halogen Headlight Bulb Replacement
Head/Tail/Brake Light LED Replacements thread Brett: "LED headlight bulb test: Now with Pictures!"

Ignition switch

  • Two Brown/White wires go on one of the switch's twin connectors
  • On the other are two white wires and one Brown/White wire

Selenium Rectifier

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

With the (unused) lug on top up and the grounding bolt facing down:

  • White/green stripe lead goes to the clock-wise most terminal
  • The Yellow/green lead goes to the counter-clock-wise most terminal
  • Brown/white lead goes to the center terminal
  • See photos/2004/02/bat2mc/DSCN2698.jpg


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

Installing Ignition Coils

  • Clamps around coils are mounted beneath the brackets that mount to the frame
  • Don't over-tighten clamps - ruins coils
  • Use Loctite
  • Mount coils as far to rear as possible without interfering with the head steadies - too far forward will interfere with gas tank - about 5/8" between blank end of coil and the bracket

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:

  • Between low tension terminals (-/+): 1.5-2.2 Ω
  • Between low tension terminal (- or +) and high tension terminal: ~4 KΩ
  • Between case and any terminal: ∞Ω

Resistance readings for 12v coils:

  • Between low tension terminals (-/+): 4.-4.5 Ω
  • Between low tension terminal (- or +) and high tension terminal: ~4 KΩ
  • Between case and any terminal: ∞Ω

Ignition Coil Wiring Connections

With Pazon

Left Coil (DS)

  • Black from module to -
  • Black lead from + to TS coil -

Right Coil (TS)

  • Red from module to +
  • - From + of DS coil

With Repro Harness (2006)

Left coil

  • White x2 (top) inboard (-) (1 on original coils)
  • White (bottom) inboard (-) (1 on original coils)
  • Black/White x2 outboard (+) (15 on original coils)

Right coil

  • Black/Yellow x2 (red tie) inboard (+) (15 on original coils)
  • White x2 outboard (-) (1 on original coils)

With Original Harness


Left coil

  • White x2 on top (-) (1 on original coils)
  • Black/White on bottom (+) (15 on original coils)

Right coil

  • Black/Yellow on top (+) (15 on original coils)
  • White on bottom (-) (1 on original coils)

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

Pazon PDF Installation, timing, and trouble-shooting

Pazon Schematic Diagram

Pazon - Troubleshooting

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 "How to Troubleshoot a Boyer Ignition" Includes good info relating to all EI systems

Podtronics Rectifier/Voltage Regulator

Instructions & Diagram Podtronics Home Page
Rectifier/Voltage Regulator Installing beneath battery carrier



  • Oil leak btwn head and cylinders - dissappeared with re-torque
  • Oil leak from cylinder base - removed head and cylinders and replaced torn base gasket
    Procedures and Completion Times:
    • Remove tank/carbs/exhaust - :13 minutes
    • Remove head steadies/rocker boxes - :43
    • Remove head - :50
    • Remove cylinders - 1:35
    • Clean everything up, inc. old gaskets - 4:00
    • Reassemble everything/adj valves - 2:45
    • Total time: 10:06
  • Staccato exhaust note after adjusting valves - T.S. carb nipple was raised and cocked, giving more throttle to that side
  • Lost footshift lever twice, once in Derby Line and again outside of Ayer's Cliff. Lost the original bolt :( the second time and had to climb the driveway in second gear. Replaced with 1 U.H. 1/4" x 28tpi and lots of blue loctite.


  • Speedo gearbox turned with wheel
    * Use pipe to hold on brake while tightening axel nut
  • Tire rubbing chainguard
  • Idle goes up when throttle rolled forward (D.S. carburetor)
    * Worn out airslides - resleeve carburetors

  • Couldn't get new points OR Pazon to work
    * Problem was a bad spark plug
  • Lost "seating nut" for top lug pinch bolt


First run (2 miles - Chemin Vallieres)

  • High revving

Second run (5 miles - Ayers Cliff)

  • Engine missing severely (electrical)
  • Dead battery

Third run (28 miles - Tyson's Corner)

  • Road grader dust!
  • Running hot?
  • Quite a bit of oil out of fender breather pipe
  • Primary chaincase leaking?

Fourth run (50 miles - Sherbrooke)

  • Lost (and found) gearshift lever (again!)
  • Stalls coming to a stop
  • Running hot?
  • Quite a bit of oil out of fender breather pipe
  • Still leaking from primary chaincase?

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

  • Lost screw, washer, and clips for exhaust valve inspection caps
  • All rocker box cover nuts and bolts were loose, with one backed right out
  • Head steady nuts were loose
  • Less oil out of fender breather pipe today
  • Seems not to be leaking from primary chaincase drain after tightening the bolt


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

  • Speedo illumination lead flopping about and shorting out all around the upper triple tree.
  • Shorting out of low tension wires to points due to my not having tightened the small nuts which hold on the leads and the points - one had fallen right off and was lying at the bottom.

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


  • Acid spilling from battery
  • Sticky throttle cable
  • Running rough
  • Leaking crankcase oil from hoses
  • Lost right-hand stanchion tube cap
  • Lost gear-shift lever
  • Nearly lost kickstart lever
  • Frame paint disintegrating
  • Never got the "Sleeve nut" #40 on page 55 of #7 parts book. Stock number F8034
  • Integrity of front end? Have the replacement circlip but have not installed it
  • Missing small washers that were between brake switch and chainguard

About The Bonnie Ref

The Bonnie Ref is the culmination of my quest as a non-mechanic to maintain and repair 'Bonnie', my 1969 T120R Triumph Bonneville. Along the way I benefitted tremendously from the knowledge of fellow CVMG club members, the BritIron mailing list, and eventually classic Triumph forums like those at and

I made my notes in HTML and used hyperlinks to organize and present the info. Tired of the often useless and confusing illustrations I found in workshop and repair manuals I created my own using Fireworks 2.0 (just say no to Adobe) and digital cameras. Eventually I began also including links to info from sources far sager than myself.

Corrections, suggestions, and comments are welcome: tmc at

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 which 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 your source. So, in October of 1968, Bonnie was either the 24th or 25th twin produced by Triumph under the new system.

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

I've styled Bonnie to look more like the 1966 models I had 'back in the day'. Mainly, fitted retro tank badges and stainless steel fenders, yanked the zenner diode out from beneath the headlight, added a steering damper, and dispensed with the exhaust balance tube. All original parts - tank badges, fenders, seat, exhaust & mufflers, handlebars, carburettors, points, etc. are conserved, so possible to restore to near-original condition.

Bonnie's Back Pages Index