To prevent the generation of stay of the fuel inside of a heat insulating pipe or an intake pipe, and prevent the generation of operation stop of an engine when the engine is inclined by providing plural axial grooves, which is formed deeper, as it comes close to an engine, in the inner peripheral wall of a heat insulating pipe for connecting an intake passage of a carburetor to an intake port of the engine.

When a throttle valve 47 is turned to the accelerating direction, open degree of a throttle hole 47b communicated with an intake passage 16 is increased, and open degree of an injection hole 56a is increased with a rise of a needle valve 55 from the injection hole 56a of a fuel injection nozzle 56, and the predetermined quantity of the fuel is sucked. In a film type carburetor having such a structure, plural axial groove 65, which are formed deeper, as they come close to an engine, are formed in the inner peripheral wall of a heat insulating pipe 63 with an equal space in the circumferential direction. With this structure, at the time of idling operation of the engine, the fuel adhered to the inner peripheral wall of the intake passage 16 and having a specific gravity larger than that of the intake air is flowed into the axial groove 65, and the generation of sudden suck of the fuel is prevented so as to prevent the generation of engine stop due to the supply of the rich air-fuel mixture to the engine at a stroke.