To improve startability of an engine by operating an actuator by an intake pipe pressure at the time of start of the engine, operating the power fuel supplying means of a carburetor through a link mechanism, and supplying power fuel from the power fuel supplying means into an intake system for a prescribed fuel supplying time.

At the time of start of an engine, a starter motor is cranking- operated so as to increase the negative pressure condition of intake pipe pressure. In the case where a start time is in a extreme low temperature condition, intake pipe pressure is acted on the pressure chamber 38 of an actuator 34 by a transmitting passage 52 through a temperature sensing means 56 and a throttle 54. A rod 42 is removed by intake pipe pressure simultaneously with movement of a diaphragm 40, the piston valve 18 of a power supplying means 12 is pushed up by the movement a jet needle 28 is pushed up, and then power fuel is supplied into an intake pipe 4. When a prescribed fuel-supplying time is passed, force for pushing up the piston valve 18 by the actuator 34 is powered down so as to push down the jet needle 28.