| 摘要 |
An SOHC type internal combustion engine comprises a pair of intake valves and a pair of exhaust valves, which are carried in a cylinder head, for opening and closing operation, at a small angle formed by axes of both the pairs of the valves in a projected view on a plane perpendicular to a crankshaft axis including an axis of a cylinder, a single cam shaft rotatably disposed above a combustion chamber, a single rocker shaft fixedly disposed above the combustion chamber, a plurality of intake rocker arms interposed between the cam shaft and the pair of intake valves and swingably carried on the rocker shaft, a pair of exhaust rocker arms interposed between the rocker shaft and the pair of exhaust valves and swingably carried on the rocker shaft, and a plug insertion cylindrical portion which is provided in the cylinder head between both the exhaust valves and into which is inserted a spark plug disposed at a substantially central portion of a ceiling surface of the combustion chamber. In this SOHC type internal combustion engine, a connection changeover mechanism is provided in the plurality of intake rocker arms for changing over the connection and disconnection of adjacent ones of the intake rocker arms to change the operation mode of the intake valves in accordance with the operational condition of the engine.
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