Final Drive -
I always knew that this would involve some juggling to get the chain run correct as the stock YPVS front and NC30 rear sprockets were around half an inch out of line.
This special front sprocket from an outfit called Fast from the Past in the States deals with most of it - it has an offset of 10mm and I managed to squeeze another 1mm by putting a shim in behind it without losing the engagement of the lock washer on the end of the shaft -
Talon engineering in the UK actually make a similar sprocket but they haven`t been replying to calls or emails for the last four months so I have to assume that they have gone out of business which left me the choice of buying one from a European supplier for about £80 or an American one for half that price.
I have regained another 2mm of the offset with some subtle machining of a Talon 520 rear (luckily Dennis Trollope had one on the shelf) -
I don`t think that the gold sprocket really suits this build but I`m stuck with the compromises of limited choice -
This is a workable solution but something I may have to revisit later. I have fitted a heavy duty non O-ring race chain with a clip link for now as I will need to check the chain clearance when we re-route that left side exhaust tail pipe.
Stock gearing on a 350 YPVS is 17/39 but that`s a bike which makes 60 bhp, weighs 145kg and has an 18" rear wheel - this bike will potentially make 80bhp, weigh 120kg and has a 17" wheel, each of those factors would warrant higher gearing in it`s own right so all three together certainly will.
I have no choice with the front sprocket which is only available in 17t from any source - 38t is the smallest `off the peg` NC30 rear so that`s what I`m going with for now but I fully expect to be needing a smaller, custom made rear further down the line.
Putting the chain and sprockets on has enabled me properly to test the gear selection with the Chinese `uprated` cam and detent arm and I have to report that it is so bad that I am going to strip the right side of the motor and put the stock parts back in - yes the location in each gear is positive, so positive that the force required to shift is nearly enough to bend the gear lever, also the neutral detent position is so tenuous that it takes half a dozen attempts to find it and as soon as you turn the rear wheel of touch the kickstart it drops straight back into first.
We live and learn...
