Abstract: A motorcycle engine having an exhaust passage air introduction system. Each cylinder includes two exhaust passages which are joined at a point displaced from the engine. Air is introduced into one of the exhaust passages of the two so as to more fully combust the unburned gasses within the exhaust passage and then to more fully combust the unburned exhaust in the joined passage. The timing of the valves associated with each exhaust passage is such that the valve associated with the passage having the air inlet has advance timing. A chain tensioner for the timing chain includes a tensioner cylinder hydraulically actuated by the engine oil. A gasket having an orifice therein is positioned between components in the oil passageway extending to the tensioner cylinder. The oil cooling system of the engine includes an oil filter and an oil cooler which are displaced from one another and mounted to a common base which is in turn mounted to the engine.

Abstract: An evaporative fuel processing apparatus for a two-wheel vehicle provided with a separator for separating an evaporative fuel from a fuel tank into a gas and a liquid. The apparatus comprises a bent conduit in fluid communication with the separator having opposite ends, one of which is opened near a tank cap mounting portion at an upper portion of said fuel tank and the other passing through the fuel tank to communicate with an absorber floor. A tank cap may be directly coupled with the separator in a second embodiment. A roll-over valve may also be employed. A gas-liquid separator may be integrally formed in the cap.