Abstract: A V-type two cylinder engine is transversally mounted by being supported between a truss frame and a body frame while the front cylinder is inclined forwards below the truss frame. A radiator is arranged above and in front of the cylinder head of the front cylinder. A fuel tank is mounted over the truss frame. A reserve tank is arranged in a sideways space inside the truss frame on the side opposite to the side to which the front carburetor on the top of the front cylinder is offset. The main body of the reserve tank is formed so as to extend from the front upper side to the rear lower side along the truss frame. The reserve tank has a water supply port projected upwards, so that the upper end of the water supply port, i.e., the water supply opening (cap) is arranged above the truss frame and under the fuel tank.