Patent ID: 7578213

Claim:
An engine for a motorcycle, comprising: an engine case splitable into an upper case section and a lower case section; a crankshaft and a transmission input shaft extending in a width direction of the motorcycle and rotatably supported at a mating surface constituted by and between the upper case section and the lower case section; and a transmission output shaft rotatably supported in the lower case section to be rotatable by the transmission input shaft, wherein one side surface of the lower case section has a circular transmission-output-shaft insertion opening through which the transmission output shaft is inserted in the lower case section of the engine case from an outside thereof, wherein said circular transmission-output-shaft insertion opening is provided entirely in said lower case section, an eccentric bearing holder for holding a bearing that rotatably supports one end of the transmission output shaft is mounted in the transmission-output-shaft insertion opening in a detachable manner from the outside of the engine case, and an axis of the transmission output shaft deviates from the center of the eccentric bearing holder toward the transmission input shaft.