Power unit and staddle-type vehicle provided with the power unit

摘要

A power unit for a small vehicle, comprising an engine; a V-belt type continuously variable transmission including a primary sheave, a secondary sheave and a V-belt wound around the primary and secondary sheaves to transmit rotational power therebetween; a rotational support member provided on an outer surface of a crank case and connected to a vehicle frame via a pivot shaft penetrating through the rotational support member in a vehicle width direction such that the rotational support member can pivot; and a groove width controlling mechanism for controlling groove widths of the primary sheave and secondary sheave by applying arbitrary shifting thrust to the movable flange of the primary sheave using an electric motor, wherein the engine having a cylinder body, in which an angle formed between an extension of a straight line connecting between a driven shaft of a driven side sheave and a drive shaft of a drive side sheave and a cylinder axis is 45 degrees or less, the electric motor is arranged on a front portion of an upper surface of the crankcase, the starter motor for starting the engine is arranged at a lower portion of a back surface of the crankcase, and a rotational support member being positioned below an underside of the cylinder body.