With factories in turmoil and sliding to oblivion, the ACU had to look elsewhere for ISDT team bikes… enter the Cheney Triumph.
The world yelled ‘lightweight’ the British said ‘Cheney dear boy’ and created a legend in ISDT, we look at the ex-jim Sandiford 504cc ISDT Gold Medal winner.
Sometimes the best looking motorcycles are created by accident or necessity rather than by design. For instance had the Mccandless brothers not felt Norton’s post World War Two trials bike was a bit unwieldy and set about creating their own from Norton parts, then the 500T would not have seen the light of day. Road enthusiasts can point a finger at Eddie Dow’s conversion of a BSA A10 to Goldiesque style which forced BSA’S hand to produce the Rocket Gold Star. In the same way a need for ISDT success and the lack of a suitable standard product led to the introduction of the Cheney Triumph and created an ISDT legend, replicas of which are highly sought after.
In 1970 the rules for the ISDT changed to reflect the turmoil in the motorcycle industry worldwide. Since its inception in 1913 the International Six Days Trial had included a Trophy and a Silver Vase competition within its framework. The Trophy was the premier contest with participants mounted on machines made in their home country. The Silver Vase contest allowed riders to use any machine. As the worldwide industry was shrinking, this meant the Trophy contest had fewer and fewer eligible teams and the Silver Vase was being seen as the more desirable contest. So to counteract this, both contests were thrown open to national teams mounted on any make of machine.
However, the Triumph unit twin engine had a good reputation in the ISDT – fast, flexible and reliable – all it needed was to be mounted in a more suitable frame than the stock Triumph one. The MX world had been using after-market frames for years and Eric Cheney’s chassis had a good reputation. With Bsa/triumph unwilling or unable to supply complete bikes the answer was to fit a twin engine into Cheney’s frame.
However, it was not to be quite that simple as outside factors conspired to delay the construction of the bikes. The biggest of these problems involved a strike at the Dunlop factory which held up the supply of the correct high tensile steel rims. In the end a wheel building specialist came to the rescue and sourced enough rims from his own stock to complete the job. Cheney and his team worked flat out the weekend before the Welsh Two-day Trial so the team members could test their machines.
The bikes themselves bristled with the special requirements of an ISDT rider and a lot of thought had gone in to their construction. Starting with the Cheney oil-bearing frame, a centre stand had been added so wheel changing was easier and rock guards added to protect the engine. Cheney’s front forks were used and his own Elektron front hub too, while at the rear was BSA’S crinkle hub – a long time favourite for such machines. Internally the engine was to Triumph’s Daytona specification but with a lower first gear ratio. In their feature on the machines in 1970 Motorcycle revealed all machines for the Welsh would be 490cc but after the event two would be enlarged to 504cc for use in the 750cc class and all bikes would have their compression ratio lowered to 8:1 from 9.5:1 as it was felt the fuel available in Spain where the ISDT was