The Triumph TR6 was launched in 1956 as the 650 cc companion to the TR5 Trophy. The Trophy had been known as a Trials bike with a wide-ratio gearbox and low final gearing. The TR6 was fitted with the Tiger 110 engine, alloy head and same higher compression ratio as the Tiger and with a single carburetor. Both models were moving away from Trials into street scramblers. For 1957, the TR6 got the Tiger’s eight-inch front brake, while the TR5 kept the smaller seven-inch unit.
Both models got the new slick-shift gearbox in 1958, but the TR5 was dropped at the end of the year. The TR6 was given a new duplex frame for 1960, and an alternator replaced the generator. In 1961, the TR6 essentially became a single carburetor T120 for the rider who didn’t want to fiddle with balancing two carburetors. The 1962 TR6 S/S was fitted with siamesed exhaust and low silencer on the right.
Unit construction was adopted across the lineup of big twins in 1963, and the 6T Thunderbird, T120 Bonneville, and TR6 Trophy shared an entirely new frame while retaining the same engine, forks and wheels. The new crankcase divided along the engine center line, but the joint was moved to the right so the gearbox lay in the right case half.
Front forks were revised for 1964 and the TR6 gained twin pipes and silencers, like the T120. Changes for 1966 included an eyebrow tank badge and 12-volt electrics.
There were significant differences between the TR models sold on the East and West coasts, enough that a booklet even described them. While the T120-based TT Special off-road competition bikes were built from 1963, a single-carburetor TR6SC model was offered on the West Cost by Johnson Motors from 1961-66 for desert racers.
Although TR6SC engines were stock, everything possible was removed, and the bikes ran with open pipes and a lower final gear ratio. Alloy fenders and a skid plate were fitted and for the final year of 1966, both TR6SC pipes ran together on the left side.
Both T120 TT and TR6SC models were extremely competitive desert racers until the rise of the lighter two-strokes, and equally hard to beat on Grand National flat track races. Numerous races and championships were won on both models by legendary riders like Bud Ekins, Eddie Mulder, Gary Nixon, Dick Mann and Skip Van Leewen, among many others. Even Steve McQueen won the 1963 Novice Class at the National AMA Cross Country Championships on a TR6.
From 1967, the TR6 shared almost everything with the T120 Bonneville until the end of both models, at the adoption of the oil-in-frame design in 1971. Valve sizes were increased, and forks, brakes and gearbox were improved. The principal distinction, apart from available colors was the choice of one or two carburetors. Many collectors consider the 1967-70 bikes to be the best.