To improve workability of a connection surface arranged on a crankcase in a power unit for loading vehicles which contains a transmission gear including a V-belt type continuously variable transmission having a driving pulley mounted on one end part of a crankshaft in a transmission case at least a part of which is constituted of a cover and a case part connected to each other, where the connection surface for connecting a cylinder block is arranged on the crankcase and the case part extending outward from the outside surface of the cylinder block is arranged in one component.

Within a range where a part of the crankcase 21 provided with the connection surface 36 is projected in the axial direction of the crankshaft 25, the peripheral surface of the case part 56 extends from a part corresponding to a driving pulley 67 to the cover 57 side end of the case part 56, has a plane surface part 95 parallel to the connection surface 36, and forms no protruding part closer to the cylinder block 22 than a plane surface L including the connection surface 36.