Motorcycle transmission

Claim 1

A motorcycle comprising: a motorcycle frame; front and rear wheels rotatably mounted on the frame; an engine mounted on the frame; first and second shafts respectively coupled to the engine and rear wheel; a first pulley means including first and second pulley sheaves rotatably fixed to said first shaft, said first pulley sheave axially slideable on the first shaft, said pulley sheaves having cone-shaped faces; a second pulley means mounted on said second shaft; a belt extending around said first and second pulley means to transmit power therebetween; a cam member fixed to the moveable pulley sheave on said first shaft; a second assembly including a support fixed to said first shaft and a plurality of centrifugal weights pivotally mounted on the support and having first end portions engaged with said cam member, said centrifugal weights being urged to pivot by centrifugal forces, when the support rotates, so that said end portions press against the cam member with a force that increases with rotational speed of the first shaft, said force urging said first pulley sheave towards said second pulley sheave; and a spring preloaded to urge said second pulley sheave away from said first pulley sheave; said cam member formed with predetermined engagement and top speed cam regions that sequentially engage the centrifugal weights as the moveable pulley sheave moves sequentially from an engagement position wherein the force of the centrifugal weights thereon first exceeds the preload of said spring so that the cam member and moveable pulley sheave begin to axially slide, and a top speed position wherein said pulley sheaves are closest together; the face angle of said cam member, as measured between the radial direction to the axis of the first shaft and imaginary lines normal to the cam face, increasing from less than 45* at said engagement position to an angle of 45* at an intermediate position, and a predetermined high angle of more than 45* at said top speed position, the axial distance K2 between said intermediate position and said top speed position being less than one-half the axial distance K1 between said engagement position and said top speed position; said cam member being formed so the face angle changes from 30* to 60* along an axial distance K3 which is less than one-third said axial distance K1.