When Triumph’s Trophy Trail first hit the dirt roads, ISDT riders rapidly made modifications to improve its performance. Roy Maddox meets an owner who’s continuing that grand tradition with his own 500 twin…
When Triumph's Trophy Trail first hit the dirt roads, ISDT riders rapidly made modifications to improve its performance. Roy Maddox meets an owner who's continuing that grand tradition with his own 500 twin ...
Back in the 1960s, our American cousins were good customers for Triumph’s off-road oriented machines, but sales of the highpiped street-scrambler T100C models had dropped off with the advent of cheaper Japanese trail machines. However, the marketing suits at the Meriden factory figured that a Triumph-powered trail bike might still have good sales potential, so they built one.
Introduced for the 1973 model year, the Trophy Trail was known as the Triumph Adventurer in the UK. Rumour had it that the Trophy Trail was actually a tribute to the 1973 International Six Days Trial (ISDT) that was being held in the US; the first time since 1913 that the ISDT had been run outside Europe.
The ISDT was originally intended to be a reliability event, with the motorcycles running for six days, and repairs could only be done by the rider with tools carried on the machine. This made a great deal of sense back before World War 1, as roads were in pretty rough shape. After the end of WW2 the event had been altered to fit a more modern format, with the course being run mostly on dirt roads and trails and a bit of tarmac in order to keep everybody honest as to lights and braking. Many manufacturers took winning deadly seriously, but not the boys designing the TR5T. This new model was not intended to go up against ferociously focused machines put forth by outfits like Jawa, Husqvarna and KTM, but would be the layman’s version, providing the image while offering a modicum of comfort.
The TR5T has a 490cc, over-square engine (larger bore than stroke, in this case 69mm bore by 65.5mm stroke), detuned a bit from the twincarbed T100R Daytona version in order to give the machine more tractability. Compression was a moderate 9:1 and carburetion was by a single 28mm Amal Concentric. This provided satisfying throttle response for greenlaning or to plonk along dirt roads, with a claimed 30bhp at 7500rpm. A savvy rider would keep the tacho between 3000 and 5000rpm, which offers sufficient torque at one end for rapid(ish) progress and acceptable vibration at the other.
The key to the Trophy Trail’s climbing and slogging abilities can be found in its gearing: it came stock with an 18-tooth gearbox sprocket and a 53-tooth rear sprocket, a combination that worked well with the bike’s 4-speed gearbox. Claimed top speed when the bike debuted was a teeth-rattling 75mph, predictably slower than its sporting Daytona sibling, which was good for over 100mph.
Ignition is by coils and points, with a 12V battery and an alternator. Of note is the exhaust system, with header pipes coming out of the cylinders to be siamesed as they disappear behind a small skid plate and run below the engine into a fabricated silencer that mounts under the right-side swinging arm. There is nothing round, smooth and chromed about this silencer. Instead it is an efficient, flat-black, elongated box that had to be acceptable to the US Forestry Service.
The chassis is a pretty good frame, a variation of the one used on the BSA B50 singles that appeared in 1971. At the Triumph plant in Meriden a B50 frame was brought in, a few alterations made to the mounting points, and the Triumph twin bolted in.
The swinging arm uses the BSA motocross method of chain adjustment, with the entire swinging arm moving fore and aft via snail cams at the pivot point rather than merely pulling the wheel back. Though fine for a race, it certainly wasn’t built for six days of hard duty and an inevitable tyre change or tyre repair, which means that the wheel isn’t quickly detachable.
The front tyre is a 3 by 21-incher, and the rear a 4 by 18-inch. Brakes are a limiting factor, with a skinny sls 6-inch drum on the front and an 8-inch drum on the back. The three-quarter-length saddle is nice and flat, good for moving about on. Despite the presence of passenger footrests, the TR5T is best considered a solo machine.
The petrol tank holds just 2.4 gallons, but thanks to good fuel mileage that’s enough for more than 100 miles. A smallish headlight keeps the demons of night at bay, and a speedo and tacho are sensible instruments, though the tacho is barely necessary, as the solid-mounted engine tells the rider when it’s time to shift. Wet weight is in the vicinity of 350lb, heavy for a real dirt bike but light enough for a road machine.
When the TR5T was introduced in September of 1972, Triumph had its eye on the ISDT and had a dozen bikes prepared for the Berkshire USA event, half for the Yanks, half for the Brits. The British ISDT team came in second overall and individual riders won a number of gold medals. However it should be noted that these models were extensively modified, with new forks, quick-detachable rear wheel, altered exhausts, etc.
Early on in their production, 12 rather special Trophy Trails were constructed, six for US riders selected by Triumph and the remaining six for Britain’s Trophy and Vase team members. Prep work for all 12 took place in Baltimore and it soon became apparent that it had it had been a very thorough job. They were still recognisable TR5T models but the front forks were now Italian Betor units with quick-release Rickman conical hubs. Lightness was achieved by employing the rolling chassis of the oilin-frame BSA B50 Victor MX single mated to the single-carburettor 5TA Speed Twin engine unit. Electrics were simplified with battery-less coils and direct lighting with all equipment held under a Velcro tarpaulin triangle within the frame and complete with three coils (a spare just in case).
In customer form the Trophy Trail had a less than two-year run. By the end of 1973 the outlook at the Meriden works was so dire the factory went on strike, having built only a few 1974 versions of the TR5T. And when the factory did re-open in 1975, the decision had been made to stop production of all the 500 twins. It was the end of the line. Pity, because in its own little way, it was a fine machine. One man’s machine
As the TR5T celebrates its 45th birthday it’s become a desirable classic – after a few decades of loneliness and neglect. I have always been a fan, although never an owner, and remember being impressed with the model’s capability during my trail riding days. The original ISDT riders discovered that the Trophy Trail benefited from sympathetic modification, and the same is certainly true now that the bike’s reached its potential ‘midlife crisis’ point. Our feature bike belongs to Kevin Brown, who spends his working day at Hitchcocks Motorcycles (the superb purveyors of all things Royal Enfield) and he’s the proud owner of a much modified example of Triumph’s little gem.
He started with an original example with the intention of bringing it back to its former glory, and then Kev began imagining ways in which the TR5T could be improved. During his ownership, he’s created the perfect machine for him. While there can be no doubt that the standard of workmanship is first class and the overall effect is very pleasing to the
eye, this is no fragile show machine. It is a practical bike that is ridden to work, used for green-laning and touring.
It is actually quite difficult to find an element of Kev’s TR5 that has not benefited from his updating and modification. All of his changes qualify as improvements and to my mind he has produced the machine that Triumph could (…should…) have built. The overall impression is of a modern motorcycle with a classic heart. It’s a neat, functional, slim, shiny, capable off-road motorcycle that will cope with modern road traffic. Kev has carried out his improvements while still riding the bike, an ongoing working project. His daily experience with the Triumph led to the next improvement, and no area of the machine is free from his attention.
The front alloy mudguard has brackets underneath bonded to carry studs to fit the loop to the forks, so there are no visible fixings on the top of the mudguard. While function is very important, Kev considers the look of the thing all the time. A rightangle throttle was fitted to keep cables tidy. It was originally supplied in black and has been fetched back to the alloy and polished to house a one-off cable. Just getting the handlebars right was a small challenge, as Kev explains. ‘ The USA-style cowhorn bars pulled back too far and were too high. I got some trial-style bars and cut about 30mm off each end, drilling them to pull the wiring through.’
The seat, sourced from Hitchcocks’ stock, has been modified with alloy brackets to align tidily with the side panels. The rear rack is another one-off creation held in place with an alloy bracket fashioned from an alloy block,
and it doubles as a bungee hook. Underneath the rear mudguard an alloy tube carries and protects the wiring. The rear indicators are attached to the frame by studs and the wiring goes through the frame – no unsightly wires here. A wooden former was used to create and shape the narrow indicator design.
The rear brake is converted to cable operation with knurled knob adjuster. The front brake is the next on the ‘to do list’ with a beefier but appropriate 2ls. Kev’s plan is that the twin leading bar and adjuster will be concealed inside the brake plate: genius.
The engine also received the attention of Kev’s magical hands and was totally rebuilt, with the crank dynamically balanced. He fitted electronic ignition but was unhappy with the engine’s low speed response so reverted to points ignition and PVC coils.
‘When first using it,’ says Kev, ‘I noticed the oil at the rear of the frame never got hot. It’s lower than the point where the oil drains down the front tube to feed the oil to the pump.’ So the Triumph’s engine lubrication was improved by the addition of filters and a two-into-one oil feed which overcomes the oil-bearing frame’s low spots. ‘I made a connection via the rear drain plug through a filter to a T-section of pipe under the engine to join front and rear feeds to the pump. It now uses all the oil in the frame.’
An Amal Premier carb is fitted and breathes through a K&N filter. Says Kev, ‘My Triumph only has a nine litre petrol tank so I’ve worked to keep it economical, which meant jetting down the Premier carb. I managed (when I had no choice!) 165 miles without going onto reserve.’
The exhaust header pipes have a reputation for coming out of the head or rattling loose. So brackets were made with left and right threaded turnbuckles to tighten against the head. The exhaust and silencer is another one-off combination with a twointo-one that runs under the engine and over the cross bar of the frame. A stainless steel bracket supports the bash plate, and the
silencer was modified to clear the tyre.
The latest tweak to Kev’s Trophy Trail is an underslung handlebar mirror which was designed, created and fitted by the master fettler for safety on his next European trip. As you can see, the bike is still a work in progress, with minor modifications being made whenever the need becomes apparent.
Kevin Brown has manufactured what could be considered the perfect motorcycle. It combines the best of heritage and innovation with style and functionality. While the purists might baulk at the plethora of improvements over the original, Kevin will continue to identify the need for and devise more modifications for his TR5T – just like ISDT riders did in 1973.
Left: Kev’s TR5T when first finished. Its evolution has continued since this pic was taken, and these days it’s fitted with a different saddle, narrower at the front to accommodate owner Kev’s short legs
Above: The clean lines of the Trophy’s nearside; this machine owned by Gerald in the USA and restored with spares from BritCycle
Arthur Browning on his Triumph causes a splash during the 1973 ISDT. Arthur was an outstanding rider being successful in trials, enduro and scrambling as well as being a professional speedway rider
1973 ISDT machine shows numerous modifications, including plastic mudguards and another solution for the exhaust
ISDT Motto: ‘Be prepared’ – fitted with three coils just in case. This way you always have a spare
This truly is one wellsorted machine
Above: Some thought the silencer on the Triumph TR5T Trophy Trail 500 was clever; its location kept the rider safe from burning a leg in the event of a fall-over. Others thought it was crapRight: The 500 twin engine’s primary side receives the closest scrutinyBelow left: Neat touch: the bracket for Kev’s under-bar mirror (which doubles as a clutch lever clamp), prior to chroming
Below right: The finished mirror fitted, ready for adventure and modern traffic
This bike doesn’t sit in the shed to be wheeled out when it’s time to show off. It’s a working bike that meets the needs of the owner exactly…
The off-side shows the most work, innovation and creativity
Bonded brackets produce a mudguard with no visible fasteners
Exhaust brackets were made with left and right thread turnbuckles to tighten against the head
Compact rear end with purposeful designed and manufactured rack and indicators
Above: Kevin’s solution to the grotesque factory fitted silencerRight: A pretty power plant with modified oil lines