Patent ID: 7096844

Claim:
A four-stroke engine including: a piston cylinder; a piston located in the cylinder and movable within the cylinder; a crankcase attached to the cylinder, the piston providing a separation boundary of a combustion portion of the cylinder from the crank case; a crank member located within the crankcase and operatively connected to the piston; means for operating the engine in a four-stroke sequence; means for introducing a fuel mixture into the combustion portion of the cylinder, the fuel mixture having an ability to lubricate; means for promoting passage of a portion of the mixture from the combustion portion of the cylinder to the crankcase in a sufficient amount to provide lubrication within the crankcase without reservoir lubricant in the crankcase; wherein the portion of the mixture contains an oily substance, and the means for promoting passage of a portion of the mixture from the combustion portion of the cylinder to the crankcase promotes passage of the oily substance; and wherein the means for promoting passage of a portion of the mixture from the combustion portion of the cylinder to the crankcase includes an open gap in a piston ring on the piston.