US Patent 7588010 Power unit for a vehicle

A power unit for a vehicle comprises an engine and a transmission assembly. The engine includes a crank shaft having a rotating mass. The transmission assembly includes a drive shaft having a first drive gear and being connected to the crank shaft through a first transmission mechanism, and a driven shaft connected to the drive shaft through a driven gear that meshes with the first drive gear. With the power unit oriented such that the crank shaft is substantially horizontal, at least a portion of the transmission assembly is positioned within a region extending below a swept area of the rotating mass.