Patent ID: 6539906
Filing Date: 2003-04-01
Classification: F01L,F02B

Abstract:
A four-stroke internal combustion engine, comprising:a cylinder block including a cylinder therein and having a piston reciprocally disposed within said cylinder, said piston operably engaged with a crankshaft; a camshaft; at least one intake valve reciprocally driven by said camshaft; at least one exhaust valve reciprocally driven by said camshaft; and a vacuum release mechanism, comprising: an operating member reciprocally supported within said camshaft for translation along an axis; a centrifugally actuated flyweight member engaged with said operating member, wherein rotation of said camshaft above engine cranking speeds causes said flyweight member to move said operating member from a first position to a second position; and a vacuum release member movably supported within said camshaft and in engagement with said operating member wherein translational movement of said operating member causes movement of said vacuum re ease member, said operating member and flyweight urged to said first position at engine cranking speeds and moved by said flyweight member through centrifugal force to said second position at engine running speeds; said vacuum release member being in lifting engagement with one of said valves at said first position during at least a portion of the power stroke of said piston and out of lifting engagement with one of said valves at said second position.