Crankcase breather for two-cylinder four-stroke engine - has non-return valve formed by elastomeric sleeve to reduce crankcase pressure

摘要

In a two cylinder four-stroke engine the pistons move up and down together, and this creates considerable pressure fluctuations in the crankcase. To overcome this effect a breather (11) is fitted in a recess (13) which forms an integral part of the crankcase casting (4). The breather (11) consists of a tube with one end sealed and with perforations (16) in the wall. An elastomeric sleeve (17) covers the perforations and forms a non-return valve. The recess (11) is connected to the intake manifold and so a sub-atmospheric pressure is maintained in the crankcase.