The UK couldn’t quite leave the Triumph unit engine behind when ISDT duty cropped up – meant a few superb chassis were devised though.
As the chimes of Big Ben heralded the end of the Swinging Sixties and the dawn of what would be partially referred to as the decade style forgot, there were changes afoot – or possibly ‘awheel’ in the international enduro scene. Hitherto in order to qualify for the trophy contest, teams had to be mounted on machinery manufactured in their home country. The vase teams, plus club, military and individuals, could ride whatever motorcycle they liked. For 1970 the restriction was lifted for the trophy teams, largely at the request of the American teams it has to be said. You see, off-road sport was quite the big thing in the USA and liable to be a big money spinner.
So, despite the fact there was no actual need to ride British-built motorcycles for national honours, the home teams were mounted on what became possibly the most suitable and arguably the best-looking bikes they’d ever been issued with.
In The Motorcycle of June 1970 there was a feature on the build of these superb Triumphs by Eric Cheney and his team and it seemed the world was against the build. Almost at the last hour a supply of wheel rims had been sourced and donated on the promise the supplier – Vic Nunn Wheelbuilding – would have them replaced once supplies of the correct high tensile rims were available again from Dunlop.
With rims now on hand, the bikes could be finished for the ISDT try-out at the Welsh Twoday Trial. And what bikes they were, nickel plated frames carried oil in the tubing and housed the well-proven unit Triumph engines. For the Welsh, all engines would be 490cc but afterwards, to comply with ISDT capacity regs, two units would be bored out to 504cc. Inside the gearbox a slightly tweaked cluster would give a lower bottom gear in case of nadgery going so the bike could be plonked, clutch fully home, like a trials bike but the Daytona spec of the engine would react quickly once the throttle was wound on and the higher gears gave a decent turn of speed – so decent in fact one team member quietly told me his own similar team bike had been ‘officially’ timed at 100mph on the way to an impromptu practice session… But, we digress, feeding fuel into the engine was a 28mm Concentric carburettor protected from the elements by two paper air filters. These were easily changeable by lifting the qd seat.
For 1970 ignition and lighting had gone 12v with a pair of coils seated in a special holder designed to be easily accessible in the event of an in-event-incident. A Zenor Diode heat sink required by the extra power created from 12v electrics was attached to the front mudguard support while the capacitor used in place of a battery was mounted in the airbox on a spring. The machines featured lots of modifications to the frame which, being as it was originally an MX one, wouldn’t have or need. For instance, few MX bikes use a centrestand, none carried an air bottle for tyre inflation and rock guards too would be unusual on a MX frame.
Suspension was taken care of at the front with Cheney’s own style of telescopic fork and Koni oil filled dampers at the rear. Now the rims were available the front one was laced into Cheney’s own Elektron cast hub while the rear wheel used the very popular BSA qd hub. More oil is carried in the swinging arm tube and a small tap allows a drip feed onto the chain. Finishing off the bike was a two gallon Gold Star style petrol tank and alloy side panels which the feature claimed were anodised red.
The actual story of this bike seems a bit of a mystery and even the owner Bryn Richards is unsure exactly what it is. He’d been told at the time of purchase it was a practice or spare team bike for the UK squad but can’t find any proof other than circumstantial. He does know that when he bought the bike it was anodised blue, though colours are easy to change, and the machine had
spent a lot of time in the Isle of Man. The ISDT it had been built for was in Spain at El Escorial – and featured in the iconic film ‘On Any Sunday’ – but the bikes were also used in the Isle of Man in 1971 and some on to 1972 in Czechoslovakia. So after the destructive fire which reduced his bike to a melted ruin and required the sourcing of many parts, the finished article is as close as could be to what it was originally.
Naturally there are some discrepancies to the spec but it looks period and we hope this will suffice to keep the faith. That the frame was salvageable at all was a testament to the original build and Simon Cheney had warned Bryn it might be too far gone. A replacement engine unit, to Daytona T100 spec, was sourced and rebuilt though without the special gears. A petrol tank and side panels wouldn’t be a problem as they are pretty much stock fare for Cheney machines but neither Bryn nor Simon could quite recall what the forks were off originally but they look remarkably like the correct units. At the rear end of the machine instead of Koni dampers a pair of Rockshocks sit in place. As for hubs and rims, the front one is a miscellaneous light alloy one instead of an Elektron casting and the rear has an oil in frame conical hub with some big holes for lightening bored in. Instead of high tensile steel rims though both wheels wear alloy ones.
Though not completely original, the rebuild has kept the spirit of the era alive. Note the tortuous route for the exhaust system and the small silencer.
By all the rules there should be better engines than Triumph’s 500 for ISDT use but it has an enviable record of success. Rear brake light is well protected from the wet and the bracket is bolted to the primary case. The forks are replacements and seem to be correct but no one is sure where they originated, or more correctly which bike they originated on – bought on the internet. Hub is possibly a Grimeca Note the ISDT mods such as having a cable already in place in case the original is damaged.
Originally the bike wore Koni rear dampers but now Rockshocks sit in place. As bought and reasonably original... More cable routing, think about it, hardest job when changing a cable is to feed it through the frame and up to the bars… After the fire, showing howmuch was destroyed. Rebuild under way at Cheney’s workshop.