Subject : To dispose a starter unit and a generator on the opposite side to a speed change gear with respect to an engine to achieve equality of the weight distribution of a power unit in leftward and rightward directions and besides suppress the projection amount of the starter unit in the axially outward direction of the generator to a small amount.
Solving Means : A generator 6 includes a bowl-shaped rotor 33 securely mounted on a crankshaft 8 and having an open end directed outwardly of an engine 4, and a stator 36 supported on a crankcase 10 and disposed in the rotor 33. A starter unit 7 having a pinion gear 40 engageable with a ring gear 39, which is securely mounted in a neighboring relationship with an end wall 34b of the rotor 33, and an electric motor 43 capable of driving the pinion gear 40 is disposed in a neighboring relationship with an outer side of the rotor 33 in a radial direction.