Patent ID: 7328678

Claim:
An internal combustion engine, comprising: an engine housing; a crankshaft rotatably supported within said engine housing; a piston coupled to said crankshaft for reciprocation within a cylinder bore between top dead center and bottom dead center positions; a combustion chamber defined between said piston and said engine housing, said combustion chamber having a relatively smaller volume when said piston is in said top dead center position and a relatively larger volume when said piston is in said bottom dead center position; a camshaft driven from said crankshaft, said camshaft including a pair of cam lobes periodically engaging valve actuation structure associated with a pair of intake and exhaust valves; and a compression and vacuum release mechanism, comprising: a pair of movable flyweights; and a compression release member and a vacuum release member respectively coupled to said flyweights, said compression release member including a compression release cam and said vacuum release member including a vacuum release cam; said flyweights movable responsive to centrifugal forces between a first position corresponding to engine cranking speeds in which said compression and vacuum release cams are each positioned for operative engagement with said valve actuation structure and a second position corresponding to engine running speeds in which said compression and vacuum release cams are each positioned out of operative engagement with said valve actuation structure, and wherein in said first position, said compression release cam engages said valve actuation structure as said piston moves toward said top dead center position and said vacuum release cam engages said valve actuation structure as said piston moves toward said bottom dead center position.