Abstract: A carburetor for internal combustion engines adapted to operate normally with an alcoholic fuel. The carburetor has a slow fuel passage communicating with an idle port and a by-pass port both of which open to an intake bore at a portion of the latter around a throttle valve, a cup-shaped member disposed in a float chamber at a level beneath the level of the fuel in the float chamber and defining therein a downwardly opened space. A primary jet leading to a primary nozzle and a secondary jet leading to a secondary nozzle, which are known per se, are arranged to open, respectively, to an uppermost portion and an intermediate portion of the space in the cup-shaped member. The float chamber is communicated through a float valve of the known type with a main fuel tank storing an alcoholic fuel as the main fuel, while the space in the cup-shaped member is communicated, through a metering pump, with an auxiliary fuel tank storing therein gasoline as the starting fuel.