Abstract: A compression release device for a small internal combustion engine, including a flyweight operatively coupled to a cam member via a cam pivot shaft, wherein a lever arm associated with the flyweight is longer than a lever arm associated with the cam member, such that a relatively small component of pivotal movement of the flyweight is translated into a relatively large component of rotation of the cam member. At engine cranking speeds, a spring biases the flyweight to a first position, such that a cam surface of the cam member extends beyond the base circle of the exhaust cam lobe to partially open the exhaust valve and allow release of pressure within the combustion chamber of the engine. At engine running speeds, the flyweight is moved under centrifugal force to a second position, rotating the cam member to a corresponding second position in which the cam surface is disposed within the base circle of the exhaust cam lobe, such that combustion may occur in a conventional manner.

Abstract: An overhead cam engine having a drive train including a crankshaft rotatably disposed within a crankcase and driven by a piston-connecting rod assembly. The crankshaft drives a timing shaft at half the speed of the crankshaft through a gear set within in the crankcase. The timing shaft is parallel to the crankshaft, and has an end extending externally of the crankcase with a timing pulley mounted thereon. The timing pulley is drivingly attached through an external timing belt to a camshaft pulley mounted on an end of a camshaft which extends externally of the cylinder head. The camshaft has a pair of cam lobes mounted thereon inside the cylinder head for actuating intake and exhaust valves within the cylinder head.