Patent ID: 8689658

Claim:
A shift drum drive system for a transmission comprising a gear speed change mechanism provided in the course of a power transmission path for transmitting rotational power of a crankshaft to a drive wheel, said gear speed change mechanism being contained in a crankcase rotatably bearing said crankshaft; a shift drum constituting a part of said gear speed change mechanism and turnably borne by said crankcase; and a speed change controller configured to drive said shift drum to turn so as to cause said gear speed change mechanism to perform a speed change operation, said speed change controller including a drive means for producing rotational power and a power transmission device configured to transmit said rotational power of said drive means to said shift drum with said drive means and at least a part of said power transmission device being disposed on a lateral side of said crankcase on the side of one end in the axial direction of said shift drum; wherein said drive means and said shift drum are disposed so as to at least partly overlap with each other when viewed along the axial direction of said shift drum, wherein said power transmission device for transmitting said rotational power of said drive means to said shift drum includes a power-transmitting rotary member on one end of the shift drum, the power-transmitting rotary member being provided, at regular intervals in a circumferential direction thereof, with a plurality of engaging pins which extend parallel to an axis of the shift drum, wherein a straight line extending along an axis of rotation C 1 of the shift drum extends through said drive means.