Carburetor — general description (Audi 80 B3)

Keihin carburetor with downdraft and mechanical choke control. The primary throttle valve is opened mechanically, the secondary throttle valve is opened by vacuum created in the primary choke. The vacuum-controlled valve is moved by the pulldown unit, opening the valve under acceleration and at wide open throttle with the engine cold.

On the Keihin I carburetor, the vacuum system includes a spherical vacuum reservoir. An idle speed cutoff valve is fitted on both carburetors, and the Keihin I carburetor includes a main jet cutoff relay (photo).