Crankcase of an engine

摘要

An engine of forced air cooled type which is provided with a cooling fan fixedly mounted on an end of a crankshaft within a blower housing of the fan, and which has a plurality of meshed gears. The crankcase constitutes the lower part of the outer structure of the engine to enclose the gears and has a double-wall construction with cooling air passages thus formed therein in at least the part thereof enclosing the gears. The cooling air passages have upstream ends communicating with the delivery outlet of the blower housing and downstream ends positioned to direct cooling air against and along the outer surface of the crankcase.