Patent ID: 7779727

Claim:
A power unit case for an internal combustion engine, said power unit case comprising: a crankcase for housing a crankshaft, and a transmission case for housing a transmission mechanism, said transmission mechanism comprising: a main shaft to which power is transmitted through meshing of a gear with the crankshaft, a counter shaft to which power is transmitted through mutual meshing of a group of transmission gears with the main shaft, and a gear-ratio selecting mechanism for selecting a combination of transmission gears for performing effective power transmission from among the group of transmission gears, wherein the main shaft is arranged above a space between the crankshaft and the counter shaft arranged at a position substantially horizontally behind the crankshaft; the gear-ratio selecting mechanism is arranged above the group of transmission gears on the counter shaft whose upper portion rotates toward a meshing portion of the group of transmission gears; and wherein the transmission case comprises a ceiling surface having a lubricating projection formed thereon and projecting downwardly above the transmission gears on the counter shaft, and at a location on a ceiling surface inside the transmission case where the gear-ratio selecting mechanism is supported, wherein the ceiling surface inside the transmission case where the gear-ratio selecting mechanism is supported is formed arcuate, and wherein the lubricating projection that projects downward is formed at a lowermost portion of the arcuate surface on a rear-half of the ceiling surface.