Patent ID: 7624714

Claim:
A single-cylinder, four-stroke cycle, spark ignition internal combustion engine for mounting on a power tool comprising: a cylinder block having a cylinder, a cylinder head, a piston mounted for reciprocation in said cylinder, said cylinder head defining an air-fuel combustion chamber; an air-fuel mixture intake port and an exhaust gas port in said cylinder head; a valve cover on said cylinder head defining a valve chamber; an intake valve and an exhaust valve mounted in said intake and exhaust port, respectively, for reciprocation between port-open and port-closed positions; a valve-actuating valve train, said valve train including at least one rocker arm and at least one valve train push rod assembly extending therefrom within said valve chamber and engaging said rocker arm; a crankshaft rotatably mounted in a crankcase, said crankshaft includes a crank portion and at least one counterweight web; a connecting rod having articulated connections at one end thereof to said piston and at an opposite end thereof to said crank portion, thereby forming a piston-connecting rod crankshaft assembly; at least one cam being drivably connected to said crankshaft, said at least one cam having a cam gear and being driven at one-half crankshaft speed, the opposite end of said push rod assembly being drivably connected to said cam whereby said push rod assembly is actuated with a reciprocating motion upon rotation of said at least one cam; a lubrication oil reservoir formed below the crankcase; an oil pump connected drivably to said cam gear-cam assembly, said pump inhales lubrication oil from said oil reservoir and valve chamber and splashes the oil into the cylinder and the valve chamber to lubricate the engine parts inside the cylinder and the valve chamber.