CARBURETOR

PURPOSE:To feed a carburetor with a thick air-fuel mixture in time of complete combustion but after the combustion automatically adjust the air-fuel ratio and thereby make a smooth driving state attainable, by installing a valve which stops an auxiliary slow air bleed and feeds the carburetor with auxiliary air in time of starting. CONSTITUTION:In addition to a main air bleed 9 for a slow fuel system 8, there are provided with an atmospheric pressure chamber 17 installing an opening 18 and a diaphragm 3, a chamber 3 installing a valve 14 and an auxiliary air bleed passage 20 leading to the slow fuel system 8 via a jet 11. The atmospheric pressure chamber 17 and the downstream side of a throttle valve 4 are interconnected with each other via a passage 19 and the valve 14. In time of starting, when a plunger 10 is pulled out, the passage 20 is closed, stopping the auxiliary air bleed, and a thick air-fuel mixture is fed to a carburetor but the auxiliary air is fed out of the passage 19 coincidentally with an increase in engine speed so that there is no overthickness at all. The plunger 10 is restored to its original position in time of the end of starting whereby ordinary air-fuel mixture feed takes place.