Upper crankshaft bearing lubrication system for two-cycle engine

Abstract

The two-cycle internal combustion engine has a sump in a lower portion of the crankcase for collecting engine fuel drains and a crankshaft bearing lubrication system including a first conduit means connecting the upper crankshaft bearing in communication with the engine intake manifold, second conduit means connecting the upper crankshaft bearing in liquid communication with the sump and having an intermediate portion or reservoir, and third conduit means connecting the crankcase in communication with the reservoir. A first check valve located between the sump and the reservoir permits fuel drains to flow from the sump upwardly toward the upper crankshaft bearing in response to a suction created in response to the low pressure or vacuum in the intake manifold and prevents backflow from the reservoir to the sump. A second check valve located between the crankcase and the reservoir permits flow from the crankcase into the reservoir to pump drains from the reservoir to the upper crankshaft bearing when a high pressure condition exists in the crankcase and for preventing backflow from the reservoir to the crankcase when a low pressure exists in the crankcase.