Small four-cycle engine having compression relief to facilitate cranking

A mechanism for partially opening a selected one of the intake valve and the exhaust valve of a four cycle engine during the compression cycle, the engine having at least a cylinder provided with an intake valve and an exhaust valve, the mechanism comprising:

• a cam having a primary cam surface and a secondary cam surface located on an integrally formed fixed boss displaced laterally to the side of the primary cam surface at a predetermined rotational orientation relative to the primary cam surface;
• an exhaust valve cam follower disposed between the exhaust valve and the cam, the exhaust valve cam follower having a primary cam engagement surface engageable only with the primary cam surface, the exhaust valve cam follower oriented relative to the cam to open the exhaust valve during the exhaust cycle of the four-cycle engine;
• an intake valve cam follower disposed between the intake valve and the cam, the intake valve cam follower having a primary cam engagement surface engageable only with the primary cam surface, the intake cam follower being oriented relative to the cam to open the intake valve during the intake cycle of the engine in response to the primary cam engaging surface engaging the primary cam surface;
• wherein one of the intake valve and exhaust valve cam followers is provided with a secondary cam engagement surface displaced laterally to the side of the primary cam engagement surface and engageable with the secondary cam surface to partially open the associated valve causing the follower primary cam engagement surface to lift off of the primary cam engagement surface during at early portion of the compression cycle to provide compression relief at low speeds to facilitate easy cranking of the engine.