To improve startability of an engine by widely opening a throttle valve also at the time of a very low temperature by providing an actuator so that the advancing and retreating shaft may be opposed to a throttle lever and revolving the throttle lever in the opening direction by projecting the shaft at the time of the very low temperature.

When a temperature sensor 23 senses a cooling water temperature when an on-operation is performed for an ignition switch 23 and the temperature is judged to be -23°C or below in an electronic control part 21, when the cooling water temperature is a very low temperature, a magnetization signal is transmitted to an actuator 20 to be a solenoid valve. The actuator 20 is magnetized and the shaft 20a projects against pressing force of a return spring 20b. As a result, startability of an engine is improved by pressing a pin 4a by the tip 20b, revolving a throttle lever 4 in the opening direction, regardless of a fast idle cam 6 and a starting cam, and widely opening a throttle valve 3 up to an opening which is necessary at the very low temperature of -23°C or below.