PURPOSE: To relieve a breathing phenomenon by controlling an air quantity introduced into an emulsion tube by means of a control valve, and restricting air derived to a main well by means of an opening bored in the emulsion tube.

CONSTITUTION: An electronically controlled carburetor system is composed of a carburetor 1 and a control valve 10. The carburetor 1 is also provided with an emulsion tube 4 and a main nozzle 7. The emulsion tube 4 is provided in a main well 3 communicated with a float chamber 2, and plural number of through holes 4a to mix foams into fuel stored in the main well 3 are bored below the fuel level. An opening 4b to induce air into the main well 3 above the fuel level is also bored. The main nozzle 7 induces the stored fuel to a venturi 6. The control valve 10 also controls an air quantity induced to the emulsion tube 4. Thereby, a breathing phenomenon caused by rapid acceleration and so on can be relieved in a feedback control condition.