Patent ID: 6945201

Claim:
A method for providing positive crankcase ventilation for the crankcase of a four-stroke engine having one or more reciprocating pistons exposed on a bottom side thereof to the crankcase, whereby the crankcase and bottom side of the one or more reciprocating pistons define a crankcase volume that varies cyclically with reciprocation of the one or more pistons, the method comprising: utilizing the cyclically varying volume of the crankcase resulting from reciprocation of the one or more pistons for generating a flow of air through the crankcase; varying the flow of air through the crankcase substantially in direct proportion to engine speed; attaching an inlet control device to the crankcase for allowing a flow of air into the crankcase through the inlet device when the crankcase volume is increasing, and restricting flow out of the crankcase when the crankcase volume is decreasing; and attaching an outlet control device to the crankcase for allowing a flow of air to escape from the crankcase through the outlet device when the crankcase volume is decreasing, and restricting flow in to the crankcase through the outlet control device when the crankcase volume is increasing.