Phil,
If you have the owner's handbook, look at the illustration on page 51. You will see the kickstart has a spring loaded bendix arrangement. The spring bears on the end of the worm sleeve and creates some drag. This drag makes the ratchet pinion ride up the worm sleeve and engage with the kickstart bevel. If that spring has become worn or weakened, the worm sleeve and ratchet pinion move as a pair and the pinion doesn't engage with the kickstart bevel - hence the slippage (and bruising!). A shim washer against the end of the spring may cure the problem, providing it doesn't make the spring coil bound - in which case the kickstart will be very stiff to operate.
This job can be carried out working through the final drive aperture, but it is a bit fiddly getting all the bits back onto the shaft - especially as the kickstart gears have to be correctly 'timed' to achieve the correct 'rest' position for the kickstart lever. I find it best to use a dummy shaft inserted from the RH side, slide all the parts onto the dummy shaft, then insert the original shaft from the LH side - thus displacing the dummy shaft.
Be careful when reassembling the bendix - it is all mounted on an inner sleeve that has a cutout to clear the locking pin that is screwed in from the bottom of the gearbox case - the inner sleeve has to locate over this pin in order to seat correctly inside the 'box. The shaft that carries the kickstart gear has a flat for the locating pin - this should be positioned at 6 o'clock so that the pin prevents the shaft from turning when the retaining nut is tightened.
Regards,
Eddie.
