Transmission system with device for regulating the gear change curve

Continuously variable transmission system for a motor cycle, comprising a first drive sheave driven by a transmission half-shaft and a second driven sheave, said first drive sheave and said second driven sheave being connected to each other by a V-belt, wherein at least the first drive sheave includes a first half-sheave and a second half-sheave, substantially conical, sliding on a same axis and joined in rotation, said first half sheave being fitted internally with a speed regulator including a plurality of centrifugal masses the movement of which is able to cause an axial shift, in the direction of extension of the transmission half-shaft, of said first half-sheave in relation to the corresponding second half-sheave, a device for regulating the gear change curve provided with electromechanical actuating means for causing selective intervention of a determined group of said plurality of centrifugal masses, said determined group comprising less than all of said plurality of centrifugal masses, in such a way as to vary, for a same number of engine revolutions, centrifugal force needed to achieve the axial shift of said first half-sheave in relation to the corresponding second half-sheave.