Patent ID: 7694657
Filing Date: 2010-04-13
Classification: F01L,F02B

Abstract:
1. An engine for a motorcycle, comprising: a crank case, said crank case including an upper case and a lower case joined to each other; a crank shaft and a counter shaft parallel to the crank shaft, said crank shaft and said counter shaft being supported rotatably by the crank case; a main shaft having an axis parallel to the crank shaft and the counter shaft, said main shaft being supported rotatably by first and second bearings in first and second support walls, respectively, the first and second support walls being provided in the lower case spaced along the axis of the main shaft; and a first bearing hole for fitting therein and holding the first bearing is formed in the first support wall, the first bearing being mounted on a first end of the main shaft, a second bearing hole is formed in the second support wall, the second bearing hole permitting the main shaft to be inserted therein from a second end of the main shaft opposite the first end of the main shaft until the first end of the main shaft is fitted in the first bearing, and a second bearing is fitted and held in the second bearing hole so as to be fitted on the main shaft from the second end of the main shaft after the first end of the main shaft is fitted in the first bearing, wherein a first bank and a second bank are provided contiguously to the upper case of the crank case so as to mutually form a V shape, the second bank being disposed rearwardly of the first bank when in a mounted state on the motorcycle, and a ceiling wall portion of the upper case that covers the counter shaft from above is provided contiguously to a rear portion of a cylinder block of the second bank at an approximately intermediate portion of a slide range of a piston into a cylinder block of the second bank.