When the right frame and motor come together under one roof, there’s only one thing left to do: build the darn bike. Alas, time was not on the side of 1973’s TR5T.
Running out of road
It’s November 1972. Out of money and under pressure from creditors, BSA has shut down its mighty Small Heath factory—a plant that had once employed 13,000 people—and transferred all motorcycle production to the Triumph works at Meriden. It would be like Ford closing Dearborn, or Harley shuttering Juneau Avenue. There was no money for new product development, and the model range looked tired and stale.
You can imagine how the next part of the story might have come about, though I’ve no idea if it has any basis in fact. A few truckloads of BSA frames and running gear from the BSA Victor trail bike show up from Small Heath at Meriden’s doors. Already inside the works are a pile of 500cc twin-cylinder T100 engines that are surplus to requirements.
Some bright spark thinks: “I wonder if they’ll fit?”
So the 1973 TR5T Trophy Trail (known in the UK as the Adventurer) was born as a parts-bin special. It stayed in production for one brief year before BSA’s new owner, Manganese-Bronze, announced it was closing the Meriden factory, and the workers staged a sit-in, barricading the doors. Only the Bonneville 750 would ever be built there after that.
Little more than a postscript in the Triumph story, the TR5T combined the bulletproof 500 Twin motor in then-modern cycle parts. It’s now a sought-after rarity, and according to British motorcycle guru Frank Melling, “… one of the best bikes ever produced by the British motorcycle industry … if only it had arrived seven years earlier …”
THE TR5T STORY BEGINS IN 1957 with Triumph’s introduction of the 350cc 3TA (A for unit construction) “Twenty-one” model, Triumph’s first Twin with the transmission in unit with the engine. Motojournalists noted that the drivetrain seemed overbuilt for a 350, and the undersquare cylinder dimensions would allow for a larger displacement version with a bigger bore. They were right.
The unit 5TA Speed Twin of 1959 arrived with the same 65.5mm stroke as the 350 but with a bore of 69mm for 490cc. The sportier Tiger 100A (T100S from 1961) version arrived the following year. In North America, the T100S was available in two forms: T100S/R street and T100S/C more focused toward off-road use. The C model was intended to celebrate Triumph’s success in enduro racing, especially its wins at the famous Jack Pine event. But at first it was little more than a T100S/R with knobby tires—though it did acquire a high-pipe siamesed exhaust around 1964.
The T100S/C became the T100C street scrambler in 1967. It used a single 28mm Amal Concentric carb, and sported a pair of small mufflers mounted high on the bike’s left side, with a 5-3/4-inch headlight, no tachometer, and knobby tires—all of which said “desert sled.” Though undeniably purposeful looking, the T100C didn’t really cut it in the really rough stuff in stock form with its street-oriented suspension, but made a pleasant “dual-sport” rider. One common complaint concerned the high pipes, which made access to the toolbox almost impossible, and would require any passenger to have “an asbestos left leg,” said one contemporary test.
The T100C did eventually acquire a wire mesh heatshield over the headers and mufflers and continued largely unchanged through 1972. Fortunately, the T100 variants were spared the horrors of the 1971 Triumph 650 oil-in-frame fiasco, continuing with the lug-and-braze frame and separate oil tank. But by this time, though, lightweight Japanese two-stroke dirt bikes offered much more in performance at a lower price in the dual-purpose category.
MEANWHILE, OVER AT BSA, THE 441cc Victor street scrambler had sold reasonably well through the second half of the sixties, and got a complete makeover in 1970. The motor was punched out to 499cc and matched to a stronger bottom end and transmission. The revised drivetrain went into a new oil-bearing frame, cycle parts, electrics and forks with Japanese-influenced street scrambler styling. The 500 Victor (AKA, B50T) arrived in 1971 as a smart-looking thumper with good ground clearance, long-travel suspension, knobby tires and much better off-road riding potential. The 34-hp motor pushed out plenty of torque, but its low gearing meant it soon ran out of steam on the street. In motocross form, with a lighter frame, battery-less CD ignition and 38 hp, the B50MX motocrosser provided even better performance and more than a few competition wins. It formed the basis of the successful CCM motocross Thumpers” of the 1970s and early eighties.
But BSA’s 1972 collapse meant the B50T only lasted about 18 months. The marriage of the T100S/T100C single-carb 34-hp motor and B50T running gear, though, was inspired. The lightweight welded frame carried the engine oil, obviating the need for an oil tank; a 21-inch front wheel helped with off-road obstacles; a steel bash plate protected the engine’s underside; wide, cross-braced bars made for good steering; and the chain was easily adjustable with the swingarm mounted on snail cams.
The six-inch front brake was hardly adequate for the street, though, and the eight-inch rear meant easy back-end lock-ups; but they worked fine as long as their limitations were understood. The alloy gas tank held just nine litres, but that was good enough for 160 km, and while contemporary reports indicated a top speed of around 75 mph, vibration as much as power was the limiting factor.
And while aesthetically challenging, the square black tin muffler (with California-spec spark arrestor) mounted underneath the transmission meant no more seared shins—though its positioning did compromise ground clearance. Overall, the TR5T was a sprightly, quick-turning and nimble package weighing just 322 lbs. (146 kg)—perfect for what in the UK they call green lanes: the unpaved thoroughfares and bridle paths that criss-cross open land and border farmers’ fields.
To sum up the Triumph Trophy: if you take it too seriously as either a street or dirt bike, it’ll disappoint. But with an open mind, a sense of humour, a slower pace and some back-country trails, it could be a lot of fun.
– Triumph Trophy