Crank case of engine for motor-bicycle

摘要

An engine of a motor-bicycle is provided with a crank case which includes a transmission chamber within which a transmission mechanism and a gear change mechanism are arranged. The gear change mechanism comprises first and second shift fork shafts, a gear shift cam shaft arranged between the first and second shift fork shafts, and a gear shift shaft operatively connected to the gear shift cam shaft. The first and second shift fork shafts and the gear shift cam shaft are disposed in within the transmission chamber and the gear shift shaft is disposed externally of the transmission chamber within a gear shift shaft chamber integrally formed with the crank case and fluidically separated from the transmission chamber.