To improve riding environments by blowing passing air of a radiator to riders when atmospheric temperature is low, such as in winter.

This system comprises a radiator 11 for dissipating heats of engine cooling water; a first air exhaust port 12 installed at a position where passing air from the radiator is not blown to riders; a second air exhaust port 13 installed to the position where the passing air is blown to the riders; a first duct 14 introducing the passing air of the radiator to the first air exhaust port and a second duct 15 introducing the passing air of the radiator to the second air exhaust port; an air path switching plate 16 for setting a passing air path for blocking either of inlets of the first duct and the second duct to introduce the passing air of the radiator to either of the second duct and the first duct; a motor fan 17 installed between the radiator and the air path switching plate or in the second duct; and an air path switching plate driving device 18 driving the air path switching plate.