Patent ID: 8276472

Claim:
A transmission assembly comprising: a shift drum operable to rotate in a first rotation direction and a second rotation direction so as to engage a selected one of a reverse gear and a plurality of forward gears, said plurality of forward gears comprising a fastest forward gear; the shift drum having a reverse cam groove formed on an outer periphery thereof, and extending in a circumferential direction thereon; said reverse cam groove having a first end and a second end situated at positions spaced apart in a circumferential direction of the shift drum; and a reverse stopper arm urged by an urging member into the reverse cam groove, wherein the shift drum is configured such that at a common speed change position, in which either the fastest forward gear or the reverse gear is capable of becoming engaged, the reverse stopper arm fits into the first end of the reverse cam groove, said reverse stopper arm being operable in a manner such that: when the reverse gear is not engaged, the reverse stopper arm must be detached from the first end of the reverse cam groove, as a result of a force applied to the reverse stopper arm while the shift drum is rotated in said first rotation direction in order to engage the reverse gear; and when the reverse gear is engaged, the shift drum rotates in the second rotation direction, which is opposite to the first rotation direction, and the reverse stopper arm is in a state in which external force does not act thereon, and is operable to surmount an outer periphery of the shift drum, to move out of the first end of the reverse cam groove, and to move towards the second end of the reverse cam groove.