Importance

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Abstract

A multicylinder internal combustion engine has a valve chamber containing a valve train for opening and closing intake valves and exhaust valves, and decompression mechanisms. First, second and third cylinders are arranged in a row parallel to an axial direction parallel to the axis of a camshaft. An exhaust cam for opening and closing the exhaust valve, which is opened and closed by the decompression mechanism, for the second cylinder is not coincident with respect to the axial direction with an abutment end of the exhaust valve with which a rocker arm driven by the exhaust cam comes into contact, and is coincident with respect to the axial direction with the decompression mechanism. Thus, a space for placing the decompression mechanism is secured while suppressing increase in the length of the camshaft and in the longitudinal size of the valve chamber. Consequently, the internal combustion engine can be formed in compact construction. Interference between the pump cam and the decompression mechanism can be avoided and increase in the length of the camshaft can be suppressed by disposing the centrifugal weight of the decompression mechanism for the third cylinder at a specific position on the side of the cam lobe of the pump cam as viewed in the axial direction.

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First Claim