A water pump is disposed so as to be mounted on a cylinder head cover of an engine. An electric motor is disposed continuously from the water pump. The water pump sends cooling water to a water jacket of a cylinder block via a cooling water pipe disposed so as pass in front of the cylinder head cover and a cylinder head. In an upper end portion of a radiator, an inlet through which the cooling water is led from the engine is disposed on the left and an outlet through which the cooling water is supplied to the water pump is disposed on the right. The inlet is connected to the cylinder block via a cooling water pipe, and the outlet is connected to the water pump via a cooling water pipe.