Some motorcycles, such as 3 wheels and scooters, have dual high exhaust characteristics on CO and NOx. A mechanical exhaust gas recirculation (EGR in brief) system has been developed for motorcycles and attempt to reduce NOx exhaust emission as a valuable method. Mechanical control valve are driven by intake vacuum of the engine. Appropriate amount of exhaust gas are return to engine intake system during acceleration process and high speed condition. This system also can shut down EGR at deceleration and idling speed condition. Then, NOx and fuel consumption reduction performance was confirmed by means of experimental methods.