Triumph TR6

Sweet 1970 Triumph TR6 Trophy, with high pipes (on the other side).

THE ORIGINS OF THE TR6
The story of the Triumph TR6 starts, as does virtually every British vertical twin, with the seminal 1938 Triumph Speed Twin. This 500cc cast iron twin started it all & after WWII when civilian production was resumed, it was quickly copied by other 500 twins from BSA, Norton, Royal Enfield, Matchless & others. Triumph bored & stroked it out to a 650 in 1950 with the Triumph 6T Thunderbird. The horsepower race was on. The performance ante was raised again with the 1953 Triumph T110 Tiger, so named for its reputed ability to hit 110mph. And all this with the same old cast iron top end & one carburetor. Before long, even this wasn’t enough.

1956 Triumph TR6/B Trophy, the off-road version with 2-into-1 high pipe running along left side.

DELTA HEAD
In 1956, Triumph introduced a new aluminum alloy cylinder head, named the “Delta Head”. It had bigger valves for better flow, it was lighter & it had more fins for better cooling, which would allow higher compression ratios (now raised to 8.5:1 in non-competition bikes). It still breathed through a single Amal Monobloc carb. With the new head came a new model, the TR6.

LEAN AND MEAN
Unlike the Triumph Tiger T110 and the Triumph 6T Thunderbird, both of which came with a bulky headlight nacelle & well-valanced mudguards (fenders), the new TR6 looked very stripped down by comparison. This was meant to suit the huge U.S. market which was clambering for desert racers. The hot new TR6 not only came sans nacelle, it had slim alloy fenders & even a removable headlight, with quick-detach wire connectors. It could literally be ridden to the races, raced, then ridden home.

1958 TR6/B Trophy, with one high pipe on each side.

OFF-ROAD ROOTS
The original 1956 TR6 Trophy was intended to be a street-legal scrambler, not an all-out street bike. That was the territory of the Thunderbird (touring) & Tiger (sport). In fact, the TR6 was quickly named the “Trophy-Bird” because, in the public’s eyes, it was a cross between the off-road Trophy 500 & the 650cc T-bird. Of course, most people who bought a Triumph TR6 didn’t strip it down & race it. Most were perfectly happy with the TR6 as a lean-looking street bike. The look stuck & became the trademark look of fast motorcycles from then on. Interesting to note is how Triumph itself, the authors of this new look, missed it altogether with their next big performance bike, the 1959 Triumph Bonneville, which came dressed out more like a 6T Thunderbird, with big fenders & a nacelle. It only took them one year to see their mistake & by 1960, the Bonneville looked just like the TR6, but in different paint combos. From that point on, the Triumph TR6 & the Triumph Bonneville became sister-bikes. In fact, many considered the TR6 to be a “Bonnie with one carb”, and this was pretty much true. But the TR6 came first & established the look, so perhaps a more accurate description would be that “the Bonneville is a TR6 with two carbs”.

1961 Triumph TR6C Trophy with one high pipe on each side.

MODEL DESIGNATIONS
The TR6 would borrow the name “Trophy” from the 500cc TR5. The 650cc TR6 Trophy was essentially the same kind of dual-purpose motorcycle (street & trail) but with a 650cc Tiger T110 engine in it, fitted with the new Delta Head, 8.5:1 compression (soon dropped to 8:1), E3325 sports cams & single 1-1/16″ Amal Monobloc. Before the first year was up, Triumph Motorcycles were already tailoring the bikes to the differing needs of the East & West Coasts of the U.S. Starting in 1957, there was a TR6A (street roadster with downpipes), TR6B (with a 2-into-1 siamesed exhaust like the ’56) and a TR6C (for “Competition” or off-road). The TR6 was the hot rod of the Triumph line & as such received constant refinements to its non-unit-construction engine, primary & gearbox through 1962. But big changes were coming. One thing that never changed however, was that a TR6 always had one carburetor & a Bonneville always had two. Pre-unit TR6s were known as “Trophy”, but after the unit-construction machines arrived in 1963 & the Triumph Tiger T110 disappeared, the street version of the TR6 became known as the TR6 Tiger & the street-scramblers with high pipes were called TR6 Trophy.

This 1963 Triumph TR6SS is the first year for unit-construction.

UNIT CONSTRUCTION ARRIVES IN 1963
At the close of the 1950s, Triumph & most of the British motorcycle industry, were still building motorcycle engines pretty much the same way that they had been for 50 years. A separate engine crankcase was bolted to a primary chaincase (usually on the left), which in turn bolted to a separate gearbox, which could be rotated in its mounts as a means of adjusting the primary chain tension, all bolted together in a set of heavy steel plates. It was complex, expensive, difficult to mass produce on a large scale & heavy. And with so many joints, the whole thing tended to flex & move around with vibration & heavy loads. As power increased, it got worse. By the late 50’s Triumph had already converted it’s 350cc 3T & it’s 500cc 5T to unit construction with excellent results. Unit Construction houses all 3 major component sets (engine, primary & gearbox) in one common set of cases. It was only a matter of time before Unit Construction reached the 650 line. In 1963, the new TR6 was introduced along with the 1963 Triumph T120 Bonneville line, with their new Unit-Construction engines & a whole new frame.

ABOVE: 1967 TR6 Tiger, with down pipes.

TRIUMPH’S HEYDAY
The 1960’s were good times at Triumph Motorcycles. They were selling lots of bikes, they were popular, trendy & much sought-after. Unit Construction allowed motorcycles to be assembled faster, for less cost, than before & production shot up to meet burgeoning demand, mostly in the US. Development & refinement of the entire TR6 line continued throughout the 1960s, until it reached its zenith with the 1969 & 1970 model years, widely regarded as the best years (same for Bonneville). The 1970’s opened with Triumph on top of the world. Hopefully they enjoyed it while it lasted.

OIL-IN-FRAME FIASCO
At the close of the 1970 model year, there is not doubt the Triumph TR6 & the Bonneville needed some things. Top on the list would have been a 5-speed, a front disk brake, an electric starter, reliable electrics & a way to quell the vibration. By this time, parent company BSA had stepped in & was fouling things up via its overpriced & over-rated ‘technology center’, Umberslade Hall. This new think tank scratched the ‘wish list’ above & decided that what the Triumph 650 needed was a way to carry its oil within the frame itself, devoid of an oil tank. What’s more, this new oil-bearing frame would have to be shared by the Triumph 650 twins & the BSA 500 A50 & 650 A65. It took too long & cost too much to finish, costing valuable production time. Then when it finally arrived, it was found that the engine couldn’t be installed in the frame without first removing the rocker boxes. Even this required new rocker boxes & head bolts. But, some 11th hour workshop engineering got it done, actually improving on the old design. The new frame that started out in 1971 had a seat height of 34-1/2 inches, but was lowered to a more reasonable 32 inches. The TR6 continued until replaced by the 750cc TR7 Tiger in 1973, when it finally did get a 5-speed & front disk brake.

BELOW: 1971 TR6 with oil-bearing frame, conical brake hubs, new forks, shocks & cycle gear. Just about everything we new except the engine.

Triumph TR6 YEAR-BY-YEAR

TRIUMPH TR6, PRE-UNIT
1956-1962
Introduced in 1956 with the new Delta Head, as an off-road/enduro model only. The TR6 enjoyed great success in the late 1950s, in showrooms, on racetracks & out in the deserts of the American West.

TRIUMPH TR6,
UNIT-CONSTRUCTION
1963-1970
Gone are the separate crankcase, gearbox & primary, replaced by Unit Construction. The new engine was lighter, more compact, stiffer, more powerful & cheaper to make. An all-new frame & cycle gear too.

TRIUMPH TR6, OIL-IN-FRAME
1971-1972
While the engine carries over from 1970, everything else is new: frame, suspension, brakes & bodywork. TR6 gets 2 model years like before being replaced by the 750cc TR7.