An electronic throttle valve system more suitable for use in straddle type vehicles. A straddle type vehicle has an electronic throttle valve system for adjusting the amount of intake air to an internal combustion engine. The electronic throttle valve system includes a throttle valve, an electric motor and a control unit. A guard mechanism is provided on a valve shaft of the throttle valve. The guard mechanism includes a pulley with which the throttle cable is engaged and a lever pulley which rotates in conjunction with the opening of the pulley. A cushion spring is provided on an edge face of a notched portion of the lever pulley, the edge face generally coming into contact with a protrusion that extends from the valve shaft of the throttle valve.