1966 Triumph Bonneville, in White

1966 Triumph 650cc Bonneville T120 TT Special

Engine no. T120 TT DU31357

Frame no. T120 TT DU31357

In the 1950s and 1960s, Triumph's 650 twins were barred from AMA Class C racing, which limited overhead valve engines to 500cc. The regulations kept the big twins off the dirt ovals. There was another form of dirt competition known as TT racing – the name was derived from the British Tourist Trophy races. American TTs were held on dirt courses, but they had to have a motocross-like jump. Some courses were simple ovals with a jump, while others had left and right turns like a road course. In this form of racing, the 650 Triumphs were allowed. And they dominated.

The machine originally conceived for the purpose was the 1963 Bonneville, stripped down and tuned by west coast distributor Bill Johnson of Johnson Motors, the TT was a high performance, factory race bike, designed to fill the niche market of off-road racing.

Beginning with and improving upon their street legal Bonneville, the Triumph factory racer came with higher compression pistons, hotter camshafts and a high output ignition system, to produce 54hp at 6,500 rpm. Closer ratio gears were installed in the 4-speed gearbox, chain drive sprocket ratios were altered, and larger diameter exhaust pipes were tucked under the frame, without mufflers. Aluminum, or more durable stainless steel fenders replaced the street items, together with the 2 ½ gallon slim gas tank. Lights, fork lock and speedometer were deleted and only a tachometer was fitted. The forks received special springs and internal valving. These stripped-down bikes weighed 350 pounds, some 30 pounds lighter than the stock configuration.

The TT on offer here, hails from a San Diego collector, engineer and tinkerer. Purchased about 5 years ago from a San Diego dealer in solid original condition, in need of restoration. Starting with the engine and gearbox, both were fully rebuilt, with Bruce Barker machining parts, reportedly one of the best in Southern California. The engine with new carbs was then mounted in the original, matching-numbers frame, freshly powder coated. Paizon ignition was installed for greater reliability. The wheels were rebuilt with unpolished stainless spokes, new bushes and wheel bearings, and brakes were fully overhauled. A new, cloth-covered wiring harness was installed with a new battery. The tank was beautifully painted in the correct white and striped by local artisan, Robert Gannon.

Looking for a road-rider, lighting systems were installed and work perfectly. An NOS speedometer accompanies the original, rebuilt tachometer.

Verified by the VMCC (awaiting documentation at the time of writing), this TT Special pre-dates the “single stamp TT” of late 1966 model year. According to a registrar of the model:

From December 1965, the “T120C” stamp was demised and replaced with a “T120TT” stamp on frames and engines (from DU 31141). The T120C Competition Sports Bonneville scrambler had been demised prior to the 1966 model year, and since only the TT Special remained, a “T120TT” stamp clearly seemed more appropriate. For 1966, on engines and frames, this was created using existing “T120” block stamps together with “T” single stamps. The single stamp “T”s are – like the “C”s before them – significantly larger than the other characters, and frequently at an angle. Other than for the “TT” in place of the “C” from engines built on 9th December 1965, the stamps for 1966 model year TT Specials had the same characteristics as in 1965.

The first “T120TT” block stamp on an engine I have seen is DU39731, engine built on 26th April 1966, the last day of 1966 model year production. For the first time, the “1” in “T120” on the engine had an upper serif. The characters are all well aligned and uniformly spaced.

The last genuine stamp with the block “T120” and individual”T”s is DU39429, engine built 22nd April 1966. So, from the evidence I've seen, the “T120TT” block engine stamp was introduced in the final days of the 1966 production year, between DU39430 – DU39730.

This bike is fresh from a mechanical overhaul by a local marque expert. The bike starts easily and idles well. It is tremendously powerful with a crackle and bark from the TT pipes, especially when it comes on cam and you feel a burst of thrust. Intoxicating and addictive. It shifts perfectly through the TT specification 4-speed ‘box, via an excellent clutch with no slip. Brakes, suspension all work perfectly as does the electrical system with fully operational lights. There is no oil leak – and I have checked, there is oil in it.

With the rarity of these TTs and the number of chopped up and lost to time examples, these represent a fantastic investment. This bike is an opportunity to own a rare example with the usability of street legality.

The bike is offered on a California Certificate of Title.