An original variable valve timing mechanism with two-mode intake timing was developed according to the structural characteristics of small medium displacement motorcycle engine. Based on cycle simulation, the effects of the VVT mechanism structural parameters, control parameters and operational parameters on the engine performance were analyzed by embedding the VVT mechanism operational mode and control strategies in the engine cycle simulation. Optimum design for the late intake valve closing, the valve lift, as well as the switching speed of the VVT system was carried out. It has been proved that power and torque of the JH125 motorcycle engine can be effectively improved by loading the new type VVT system.