Patent ID: 7770481

Claim:
A transmission mechanism, the transmission mechanism comprising: a plurality of gears adapted to be configured in a plurality of gear positions, a shift drum apparatus; a support shaft; a shift fork slidably mounted on the support shaft, the shift fork provided for selectively changing a gear position; a transmission case body, said transmission case body comprising: a left case half body portion; a right case half body portion; a sensor housing portion; and a groove portion; wherein the sensor housing portion and the groove portion are formed in an external surface of one of the half body portions; a gear position sensor mounted in said sensor housing portion; and a mud guard member mounted on one of the half body portions, a portion of the mud guard member configured to fit within a space formed in the groove portion and to substantially shield a portion of the side portion of the gear position sensor; the shift drum apparatus comprising: a shift drum main body formed into a hollow cylindrical shape, the shift drum main body having an end face on a first side thereof in a cylindrical axis direction, the end face open to form an opening portion, the shift drum main body having a cam groove formed on a circumferential surface thereof, an end portion of the shift fork being fitted in the cam groove such that the shift fork is allowed to slide in the cam groove; and a disc-shaped lid member press-fit into the opening portion of the shift drum main body, wherein said disc-shaped lid member is formed separately from the shift drum main body.