Altitude Compensator Circuit
The altitude compensator supplies extra air necessary to lean out the air/fuel mixture at high altitudes. The compensator circuit parallels the carburetor main metering (high speed) circuit. The altitude compensator circuit has a small separate, nonadjustable choke valve that is linked directly with the primary choke valve. This small choke valve controls the airflow when the main choke is closed. See Fig 1 .
Air flows down through a passage in carburetor main body and into a plenum chamber located adjacent to the 2 main venturi bores. A spring-loaded valve regulates the amount of air passed from plenum into the compensator body. Air flows from altitude compensator body through 2 air passages bored into the main venturi tubes.
The opening and closing of the valve in the compensator body is controlled by an aneroid bellow that reacts to atmospheric pressure. At lower atmospheric pressures (high altitude), the bellow pushes on the end of the compensator valve stem, opening the valve. At lower altitudes, the aneroid bellow relaxes, automatically closing the valve. The aneroid bellow is calibrated during factory assembly and is NOT adjustable.