PURPOSE: To improve the responsiveness of fuel supply by providing a main fuel path connecting an air bleed of a carbureter directly to a main nozzle and fuel correction path branched from the main path to be connected to the main nozzle through an electromagnetic valve controlled according to the run ning condition of the engine.

CONSTITUTION: During the running of an engine, fuel from a float chamber 14 entering a main well 20 is mixed with air flowing from an air bleed jet 26 in an air bleed pipe 18 and then injected from main nozzle 24 opening to a small Venturi section 22. In this case, are provided a main path 28 connecting an air bleed pipe 12 directly to a main nozzle 24 and a fuel correction part 30 branched from the main path 28 and connected to the main nozzle 24 through duty solenoid valve 32. And the solenoid valve 32 is controlled by ECU accord ing to the output signals of sensors for detecting the rotational frequency, cooling water temperature, intake pipe pressure, opening of a throttle valve 34, etc., of the engine.