Four stroke engine with secondary air introducing system

摘要

A four stroke engine has an engine body that defines a cylinder bore. The cylinder bore has a longitudinal axis. A piston is reciprocally disposed within the cylinder bore. A crankshaft is rotatable with a movement of the piston. A valve actuating mechanism actuates intake and exhaust valves. The crankshaft drives the valve actuating mechanism. A first portion of the valve actuating mechanism is positioned at least adjacent to the exhaust valve. A second portion of the valve actuating mechanism is positioned adjacent to the crankshaft. The engine body defines an inner passage through which secondary air flows to the exhaust passage. The inner passage has an end at a surface of the engine body. The longitudinal axis intersects the surface.