1966 Triumph Bonneville restoration


Kickstart, shift on right, drum brakes and spokes
Finally! After several months of searching I have finally found and bought a 1966 Triumph 650 motorcycle. It is a twin carburetor T120R Bonneville, the fastest stock production motorcycle in its day.

Stock 1966 Triumph Bonneville (export or US model)

(my new project)

My first motorcycle as an adult was a 1966 Triumph TR6 Trophy, which I sold after a brief summer fling with it and travelled to Europe with the money. I always regretted selling that bike and I do not even have a photo of it nor do any of my friends. A few years ago I picked up a basket case 66 Bonneville with intentions of restoring it but my fate changed when I found my BSA Gold Star and sold the basket case to fund the Goldie’s restoration.

Earlier this year I aggressively searched for a 66 Triumph, not a restored version, but a basket case, bobber, chopper, barn find etc. so I could restore it myself. A decent 66 Triumph popped up on Indiana Craigslist and I spoke with a very nice man named Dan and I bought it for $1100. It just so happened I was going to central Illinois with a large truck the following week so I drove over to Indiana to pick up my bike in person. Dan is in his early 60’s and has had a lifelong love of motorcycles. He rides a Triumph T160, is restoring a 1967 TR6 along with an Indian chief. He sold this bike to help fund his Indian restoration. It is exactly what I wanted at a great price. It has been sitting unused since 1977.

The good news is it is a matching frame and motor serial number 1966 Bonneville with a title. I have seen a lot less go for much more on Ebay recently. The motor and gear box turn freely, nearly all the black bits are included along with the correct original stainless fenders (mud guards), the one year only oil tank and front drum brake. Included, but not pictured, are the original tank badges, rear fender loop and exhaust pipes. The bad news is the seat and tank are incorrect for a 66 Bonneville, the center stand, headlight and ring, tail light, engine stays, carbs, pistons, push rod tubes and tachometer are missing. The wheel rims are crusty, one foot rest and the front fender stay are bent, the left side cover and oil tank have been chromed. Ugly handlebars, missing controls etc but to my eye it is the perfect start to my next winter project. I plan to have it ready to ride in the spring for her and my 50th birthdays.

On my long, windy drive back to Minnesota I thought about how I want to build this bike and decided to keep everything in factory stock US style condition with two exceptions which can easily be reversed. First, I’ll use the 3 ½ gallon tank and paint it as a 1966 TR6 Trophy with Pacific blue and white with a gold pinstripe complete with a parcel grid on top and secondly install a UK (home) market lower handlebar. I do not like Triumph slimline tanks, which were introduced in 66, and believe the TR6 blue and white color combination is Triumph most beautiful bike of all time. However, I do not want the white and blue fenders of a TR6 because white is very difficult to keep clean, so I’ll polish the stainless steel fenders that came with my bike. So basically this will be a bone stock 66 Bonneville with a TR6 tank and lower UK handlebars. I’ll keep my eye out for a decent original slimline tank, paint with the correct white and grenedier red stripes, and store it if I ever chose to sell this bike (unlikely).
(1966 TR6 tank, beautiful)

My goal.
I spent most of Friday and Saturday, examining the bike and breaking down the motor. I took my time, made notes, took many photographs, cleaned and examined everything, labeled and bagged all the parts and made a list of things to buy. I have the correct Triumph service tools, a hydraulic press, and an impact driver with Pozidrive bits so everything came apart easily.

I was pleasantly surprised to discover nobody has been in the lower end of this motor. The gear box and components are pristine!

The crankshaft, conrods, camshafts, tappets and main bearings are perfect. I will pull and clean the sludge trap this week and measure the conrod tolerences and replace what ever is suspect or out of factory specification. The primary is good except for the clutch basket which is on order. This is a low mileage bike that has been sitting for 40 years. The motor cases, cylinder head and rocker boxes were washed in my parts washer, rinsed with hot soapy water, scrubbed with Simple Green and a red 3M scrub pad for metal and then blasted with a combination of walnut shell and glass beads. The parts were then washed several times with hot soapy water and dried with compressed air, making sure to remove any leftover blast media. All will be sent to Green Tree Scooters tomorrow for vapor blasting.

clean and ready for vapor blasting

All the hardware will be cleaned, bead blasted and sent out to be cadmium plated as it was originally. All the black bits will be stripped, primered and repainted with catalyzed black paint. My friend Skip will install new valves, guides and seats. Once all of this is done, I’ll start going clockwise, enjoy the ride and stay tuned…
Pleased to see you've started a new project! I read (and admired) your Gold Star build and looking forward to this one too....
Great project. 1966 bikes are my favorites, I read somewhere they were the fastest most reliable of all the 60s models. I had a 66 Bonny when I was flirting with British bikes. It belonged to a Sailor who rode it between San Diego and Southern Missouri several times visiting his girlfriend. Well, the love interest faded, but he kept the bike for several years after getting out of the service. The oil tank and side cover were chromed in Mexico, but the rest was mostly stock. He took it apart, stored all the parts in cosmoline and kept it until 1980 when I bought it from him for $150. I put it together, rode it for a few months and sold it to a guy specifically looking for a 66 Bonny. Interesting enough, when I bought it the original owner had two tanks both painted dark metallic blue. One was the slimline and the other was a TR6 with the package tray. I also opted for the TR6 tank as I thought it had a classic look. Mine also had apehangers, which I changed to XS650 bars which I thought were close to the home market bends.
Even with the missing parts you did quite well for $1100, I'd have jumped on that myself. Looking forward to your build as I just acquired a 70 Tiger. Unfortunately I paid nothing for it but it came with an ultimate price, the loss of my brother to a heart attack. I inherited 4 bikes, but the Tiger will get restored and be my DD till I die. I believe everything on mine is year correct with the exception of the drag bars. 1st bike I ever bought was a 67 500 Daytona in that blue and white paint scheme that I gave $400 for in 1972. Should have them here by the end of the year.

I'm seriously thinking about restoring everything to factory stock, but I will pull the wheels and front end and set it up with a Ceriani and Kimtabs with disc brakes.
Great bit of British heritage there so jealous :p you got a real bargain too you would pay 3 times that here in UK look forward to ya progress n thread
Just looking at the pic of the white bike reminds me that the early Triumph 650's are one of the best looking bikes ever.
Signing on. Not a huge Brit bike lover, but the quality of work you turn out is too good to miss. Keep the updates coming :)
Thanks all! I am very excited about this project, I've waiting a long time for this and it feels great to start a new motorcycle restoration just as the riding season here is ending.

Quick update: The crankshaft cases, cylinder head, rocker boxes etc were shipped to Green Tree Scooters for vapor blasting, new gasket set, seals, tab washers, bearings and more have arrived. I spent several hours yesterday literally going through every part in the factory parts manual and ordered every piece of hardware that was either missing or in poor condition. Once the hardware arrives, I’ll send everything (old and new) out to be cadmium plated so everything looks as it did when it left the factory.

I cleaned the crankshaft last night, removed the con rods and bearings. I was very pleasantly surprised to find the journals to be in standard spec, look really good and will need a simple light polish. The rods are good and within spec and although the main ball and roller bearings look, sound, and feel pretty good, I am going to replace them along with new, standard sized con rod shell bearings and con rod nuts. The sludge trap cap looked untouched and came off with heat, beeswax, Kroil, impact driver and a BF Hammer. The tube was surprisingly clean, further suggesting this is a low mileage bike. I pulled the tube via John Healy’s tap and bolt method and then scrubbed the crank inside and out in the parts washer. I will install a new sludge trap and hex cap, new bearings etc and wait for my cases to come back next week or so to start going clockwise on the motor. Meanwhile, I am ordering more parts including new pistons, rings, UK made grey top seat, seat hinges, UK handlebar, grips, cables, Lucas head light and rim, rubber foot pegs etc. I did well on Ebay this week too and bought the missing cast alloy tail light shell, engine stays and bolt set all for much lower then they usually sell. I still need to find a steering damper and the correct 1966 center stand for US models using 4.0 tires. Onwards….

Thanks all! I’m still going counterclockwise… Had a good day in the shop yesterday and broke down my rolling chassis to the frame. I photographed, documented, cleaned and inspected all the hardware and parts. Some good news, some bad news, but overall I am pleased with what I have found.


All the the hardware, with the exception of two fork pinch bolts, is original and in good shape, despite the rust and dirt. No mutilated bolt heads or screws from the wrong tools.

Once I finish cleaning the frame and swing arm, I’ll put it a frame jig and test it for straightness, tweek if necessary, then finish breaking it down.

The front forks slide well, contained clean oil and should clean up well and the stations appear straight and can be re-used.

The back shocks are rough, but I’ll clean and break them down and then decide if I am going reuse them, replace the covers or replace them completely.

The hubs, brake pads, spokes, nipples are very good but it looks like I’ll need to replace the rims. They are straight and true, but too much chrome has flaked off in spots. It is cheaper to replace them then it is to have them rechromed. The wheel bearings looked great and the grease was very clean, indicating low miles and/or proper maintenance. The speedometer drive was empty, so I’ll need to buy a replacement.

I started the long process of cleaning, photographing and blasting all the hardware and black bits. I plan to burn a vacation day this week and spend it in the shop, drinking beer, listening to music and finish blasting the hardware and frame, remove the axles, tires, rims and spokes and to finish ordering missing and replacement parts. My kind of vacation.

My luck on eBay has continued and some of the missing parts have begun to arrive, including the cast alloy tail light holder.

A BritBike forum member has offered to sell me the correct tail light, steering damper and center stand at very reasonable prices. Once I finish cleaning and blasting all the hardware, I’ll do another hardware order to get the last of what I need then send it all out to be replated with cadmium. While that is out, I’ll have my crankshaft balanced to my new pistons and rings, paint the black bits and polish the covers. My parts sent out for vapor blasting should be back this week as well so I can have Skip install new valve guides, seats and valves. Despite the fact winter is just starting, I am motivated to build this bike rather quickly and have it ready for the first day of riding this spring. Onwards...
Yikes, I just spent nearly $2k yesterday on new main bearings, con rod bearings, more hardware, rear shocks, wiring harness, switches, fork parts, complete exhaust system, and much more.

Look what just arrived from Green Tree Scooters, freshly vapor blasting motor parts! This motivates me finish blasting my hardware, send it out for cad plating, and once plated, I can start going clockwise. My friend Skip will install new valve guides, valves and seats now that the head is clean. Onward!

looking good so far mate :p yup wont be long before going clockwise maybe a few more $$ first tho :eek: but see it as a investment when she's complete she gonna command her own price ;) $$$$
o1marc said:
Even with the missing parts you did quite well for $1100, I'd have jumped on that myself. Looking forward to your build as I just acquired a 70 Tiger. Unfortunately I paid nothing for it but it came with an ultimate price, the loss of my brother to a heart attack. I inherited 4 bikes, but the Tiger will get restored and be my DD till I die. I believe everything on mine is year correct with the exception of the drag bars. 1st bike I ever bought was a 67 500 Daytona in that blue and white paint scheme that I gave $400 for in 1972. Should have them here by the end of the year.

I'm seriously thinking about restoring everything to factory stock, but I will pull the wheels and front end and set it up with a Ceriani and Kimtabs with disc brakes.

Is that leaned against a Daytona :-\
Whew ...

The snow is here and it was a very busy week for me in the shop, spent mostly over the parts washer and blasting cabinet. All the hardware old and new has been photographed, degreased, bead blasted and ready to be cadmium plated. This is a long process but worth the time and effort.

Parts, old and new, are flooding in and I have bought nearly everything I need except for a new pair of Amal 389/95 monobloc carbs. Burlen/ Amal is out of stock for several months, so the hunt is on for a new pair. Britbike forum member BikeVice sold to me, at very reasonable prices, a correct centre stand, 679 Lucas tail light, Amal single pull throttle, and steering dampener. Thanks!

When my last hardware order to arrives on Friday I’ll blast the new zinc plated bits so they can be cad plated with the original hardware and everything will have the same and correct appearance.

Most of the black bits have been blasted to bare metal as well. No surprises yet and everything is in very good condition. I checked the frame and tail section in Skip’s framing jig and I am pleasantly surprised to find it straight and true to factory specs. We ran it through the jet washer at the local auto machine shop to remove 1/2” thick, 40 year old hardened grease, oil and grime. I’ll bead blast it tonight and blow out all the moisture and media before primer.

All the wheel bearings are original Swedish made SKF, show little to no wear with very new looking grease, more indication this is a low mileage bike. To be safe, I ordered new rubber sealed SKF wheel bearings.

I plan to prep, prime and paint all the black bits this weekend with catalyzed gloss black automotive paint. While I wait for my hardware to return from cad, I’ll clean and prepare the gas tank for paint and polish all the motor covers. Skip is on the road for a week or so and when he returns we can hone the con rods, install new small end bushes and he will install new Kibblewhite guides, valves and springs as well as new valve seats. The project is coming along well, and at a good pace. I will be going clockwise in a couple of weeks!
Parts, old and new, are still arriving and I still need to order a few more things like decals, lights and wiring for the gauges and new fork tubes. I thought I could clean up and use my original fork tubes, but after I dissembled the fork lowers, the left hand tube was completed rusted on the lower portion. Sigh, there goes another $100…

I shipped out 35 lbs of parts of hardware to Colorado Plating to be cadmium plated and hope to have it back before Christmas. In addition to all the parts from this bike, I included bits from two pre-unit motors, a unit motor and several pounds of spare CEI nuts, bolts and washers.

The original oil tank was heavily chromed and will need to be sent out to have the chrome electrochemically removed, but I discovered it was cheaper to buy a replacement. I picked up an ugly 66/67 oil tank on Ebay for $50 and immediately stripped off the ugly hippy paint job. It is solid with a few areas of Bondo but will be easy to refill the dents and prep for paint.

I have a busy week and will be back in the shop next week to get the last of the black bits primed and painted, repair and polish the fenders and to polish the side covers. Paint from Don Hutchinson should be here this week so I’ll to prep the tank as well. Onwards…
Another busy week, I finished blasting, primering and painting nearly all the black bits with a single stage catalyzed urethane. I am happy with the results and need to do just a little bit of rubbing and polishing on a few pieces to make them perfect. I am still working on the side cover and oil bag and will paint them both once my decals arrive.

The front drum was painted with Duplicolor wheel silver, baked in the shop oven and it looks great.

I bought a correct pair of restored Smith clocks from Ebay seller aprivatepiece aka Bobby Carter and sent him my original speedo as a core. The are beautiful (but not as beautiful as Chronometrics) and I cannot wait to see them spinning clockwise this spring.

Parts orders are coming in from the Bonneville Shop, British Only, Classic British Spares, Walrige, Tri-cor, Ebay and more sources. Paint form Don Hutchinson also arrived. Here are some of the latest arrivals: Lucas shell, rim, lamp, bulbs, wiring, ammeter, UK handlebars, black grips, wheel bearings, UK made seat, rear shocks, Lucas lighting switch, ignition and key and more. The rear rim is from Central Wheel Components via Walrige, the front rim is on back order and should be here before the end of the month. I still am looking for a pair of new Amal 389/95 (389/19) carbs Everything is here else except for decals, build holders for the clocks and a battery. Now I must wait patiently for my hardware to return from Colorado Platers so I can put this beast together. Hopefully, the hardware will arrive before Christmas.
easily my favorite builder on DTT. The nitpicking and thoroughness motivates me to be cleaner with my build
Hot off the truck (cold actually, Minnesota, it's winter...), my freshly cadmium plated hardware! I can start going clockwise on Friday. The final parts are trickling in and when I get a window of time, this bike will come together rather quickly.
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