Breather ventilation system of power-transmission casing for use in motorcycle

摘要

A breather passage is provided to perform breathing function for both two casings, one being a first casing housing therein a power-transmission means and the other being a second casing housing therein a gear-transmission mechanism. The breather passage is defined between interfacing surfaces of a main body and a cover those providing the second casing. A gasket is interposed between the main body and the cover so as to devide the breather passage into two passages. The breather passage has one end formed with a first breather hole opened to an atmosphere and the other end formed with a second breather hole opened to an interior of said second casing. The breather passage is further formed with a branch passage at the position rearward from said second breather hole to permit liquid communication between an interior of the first casing and the atmosphere.