PURPOSE: To make the whole construction of a power transmitting device compactly by installing a belt type continuously variable transmission of a power transmitting device, which is located beside a wheel disc for the rear wheel, on the side opposite to the wheel disc about the engine, and interposing a clutch between the driven pulley of this continuously variable transmission and a reduction gear.

CONSTITUTION: A swing type power unit P of a motorcycle is equipped with a transmission case T accommodating a power transmitting device incl. an engine E and a belt type continuous transmission 6 in the extent of wheel disc 5 for the rear wheel Wr. A drive pulley 14 of this belt type continuous transmission 6 is fixed in the middle of a crank shaft 12, which protrudes into the transmission case T. A sleeve 25 constructed in a single piece with the drive plate 24 of an automatic centrifugal clutch 7 is relatively rotatably supported at the left end periphery of a reduction gear input shaft 22 borne 20, 21 at the rear of the transmission case T, and the driven pulley 26 of the continuously variable transmission 6 is mounted on this sleeve 25. A geared transmission 8 is installed on the side opposite to this driven pulley 26 with the clutch 7 interposed.