The Cush - Shock Absorber system
While working on engines one sometimes comes across designs that seems to
last forever, & the cush system on the A10 must be one of them. It works as a soft
transmission between crankshaft & clutch, and the spring momentarily absorbs energy
bursts that could otherwise be damaging to most parts of the engine & gearbox. Modern
engines have some rubber shock absorption either in the clutch or in the rear sprocket.
The oil in the primary chaincase is lubricating the cush as well as the clutch
rollers & primary chain. Choice of oil is not crucial. Too thin it can leak if the
gasket & primary cover\crankcase mating are less than perfect. An old BSA book
recommended sae 50 for summer & 40 for winter, same as the engine, others use 20W50,
& some use red automatic transmission oil, fine for tracing leaks. Check all
components visually, look for loose rivets & teeth damage on the engine sprocket,
& check for free movement of the splined sliding system. Fit a new locking split pin.