The clutch weight

which is the wheel speed sensor in the continuously variable transmission system installed on the large power motorcycle

is analyzed.The displacement that clutch weight revolves around the fixed pin and the shape of cultch weight’s working curved surface decide the working radius of CVT’s driving wheel.The design of clutch weight affects the velocity ratio change of the whole system.The mathematical expression that the clutch weight has influence on the axial pressure of the driving wheel is deduced

and the mathematical expression is defined by a new concept

which is named equivalent radius.And finally

the expression of equivalent radius is improved based on the effect that the centre of mass of clutch weight and working curved surface have on the driving wheel

and the improved expression is more perfect.