The clutch on most classic bikes is fairly standard technology for it's time and is
still in use on some motorcycles today. The drive is taken through the
Primary Drive Chain to the Clutch Chain Wheel. Inside the chain wheel
are the four Driving Plates and five Driven Plates which are compressed
together by four springs acting on the Clutch Pressure Plate. There is a
rod that goes through the main gearbox shaft and this lifts the pressure
plate when the clutch lever is pulled in, therefore removing the pressure
on the Driving & Driven plates which in turn are now able to slip. In
the centre of the clutch assembly, is the Cush Drive Unit, which uses
eight rubber buttons to damp out the initial shock of the transmission
taking the power.
Tighten each nut down until the underside of the head is 1/8" away
from the top of the spring cup. The final adjustment of individual spring
pressure is best done with the engine back in the bike and with the clutch
cable attached, as the pressure plate has to be lifted and the engine
turned over to view the edge of the pressure plate.
Turn the engine over with the clutch lifted and look at the edge of the
pressure plate to see if it wobbles as it rotates.
Tighten down the nut nearest to where it is highest by half a turn at a
time and after each adjustment release and lift the pressure plate before
rotating it again. Continue until the pressure plate lifts evenly.
Next check if the is any clutch slip when turning the engine over
against compression. Tighten each of the four nuts by half a turn at a
time until the slippage is stopped.