Patent ID: 7353792
Filing Date: 2008-04-08
Classification: B62M,F02B,F16H,Y10T

Abstract:
1. An engine for a motorcycle, comprising: an engine case split into an upper case section and a lower case section, which are mated at a mating surface extending linearly therebetween; a crankshaft, a transmission input shaft and a balancer shaft which extend in a width direction of the motorcycle and are supported at the mating surface between the upper case section and the lower case section; and a transmission output shaft supported in the lower case section to be rotatable by the transmission input shaft and be disposed below the transmission input shaft, wherein the mating surface inclines obliquely forward in a side view of the motorcycle, and the balancer shaft, the crankshaft, and the transmission input shaft are arranged in such described order from a front side in a running direction of the motorcycle, and the lower case section has one side wall portion to which a circular transmission-output-shaft insertion opening is formed through which the transmission output shaft is inserted into the engine case, the one side wall portion being a side wall of the lower case section positioned on an opposite side of a clutch unit, the transmission-output-shaft insertion opening has an inner diameter set to be larger than an outer diameter of a largest one of transmission driven gears mounted on the transmission output shaft, an eccentric bearing holder is mounted in the transmission-output-shaft insertion opening in a detachable manner from outside of the engine case, the eccentric bearing holder holding a bearing which rotatably supports one end of the transmission output shaft, and an axis of the transmission output shaft deviates from a center of the eccentric bearing holder toward the transmission input shaft.