PURPOSE: To reduce the cost and projected area of a radiator by curving the center section so that both sides of the radiator may be positioned at the front section, providing cut faces which are parallel with the longitudinal direction of a motorcycle at the angle sections of both sides of a tank and also curving the lower section of the tank to inner side.

CONSTITUTION: The center of a radiator 1 is curved toward the rear side and only in the left and right direction so that the tanks 2 on both sides may be positioned on the front side. The tanks 2 on both sides are provided with cut faces 5 which are parallel with the longitudinal direction of a motorcycle at the angle sections of both ends so as to narrow the widest breath, and the outer side surfaces of the lower sides of the tanks 2 on both sides are curved to the inner side so as to be thin and narrow in width. The radiator 1 is mounted on the front side of a frame 6, faced to the front direction and is connected to the engine by a hose to circulate the cooling water. The wind produced by running is made to blow against the radiator 1 to cool the cooling water. To the front section of the frame 6, a front cowling 7 is attached, and the radiator 1 is fitted to the inner width of the cowling 7.