PURPOSE: To improve starting property by forcibly opening an inlet valve with an operating element in an engine in which the fuel is supplied from a diaphragm pump and is fed to an intake pipe through a fuel supply member having a inlet valve, and a fuel control chamber.

CONSTITUTION: A carburetor 1 for an internal combustion engine and specially for a small engine for a chain saw etc., comprises a diaphragm fuel pump 13 and a control chamber 14 in casing 11 equipped with a intake pipe 12. A diaphragm 15 is vibrated by the pressure changing of a crank case introduced to a pressure chamber 17, the fuel pump 13 supplies the fuel in a fuel storage member 16 to a fuel control chamber 14 through a fuel supply member 23 equipped with an inlet valve 25. The inlet valve 25 is actuated by a positioning lever 27 connected with a diaphragm 31. At this time, an actuating lever 45 is pivotedly mounted on the casing 11, the inlet valve 25 can be forcibly opened by operating the actuating lever 45 to actuate the positioning lever 47 through the diaphragm 31 and regulating lever 27.