Achilles Heel

Anyway, the 535cc Cheetah YPVS has an achilles heel; the transmission. In the 'Yamarilia' we ran with a 5.5-inch rear slick and there is no shock absorber in the TZ rear wheel. The only shock absorber In tre transmission Is the rubber in the clutch basket. Bear in mind that the clutch oasket and rubbers were designed for 34bhp and with the 535cc outting out approx 120bhp it used to shatter the shock absorber rubbers and basket. It gave our rider, Pat Mills, some nasty moments. I knew that using the engine in an outfit meant we were going to have to beef-up the transmission.

The 535cc Cheetah YPVS engine is a brute, producing 60lb-ft of torque with the power starting at 6000rpm and produces 20bhp extra every lOOOrpm, so the clutch has to be strong. I had an RD500LC clutch assembly on the shelf that I wanted to use because the RD500 clutch is a massively strong unit, with a proper spring-loaded shock absorber in the clutch basket and far bigger and stronger clutch plates and pressure plate. So, I contacted Graham Dyson of Nova Racing, who used to make my close-ratio gears and straight-cut gears for our LC and YPVS Formula Two race bikes, to ask if he would make straight-cut gears to adapt the RD500 clutch to the Y=>VS gearbox shaft. He produced a brilliant conversion and even converted it to run on needle rollers Instead of the standard bushes. The RD500 cluxh hub is a different spline to the 350 so I machined out the centre of the alloy hub and made a steel boss which Nova broached to the new splines. I also got them to make me a set of close-ratio gears. All in all I hoped it would be a bombproof set-up. believe Nova made a few a few others for stock.

Crankcase mouths must be machined to take the bigger barrel spigots

Straight primary gear prevents the crank winding in and out

Hineson sprung clutch basket is an off-the-shelf solution

Crankcase mouths must be machined to take the bigger barrel spigots

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