High Altitude Compensation System: Operation

The altitude compensator mixes air into the gasoline when it enters the idle/low speed circuit and main metering circuit passages in the carburetor. The metering of the air bled into the carburetor is accomplished by the use of an aneroid valve bellows, which simultaneously moves 3 spring-loaded needle valves.

As altitude increases, atmospheric pressure will exert less force on the bellows, causing the bellows to expand and mechanically open the needle valves. Fresh filtered air is supplied to the needle valves from the inboard side of the air cleaner element.

The 1987 1/2 models have one-way check valves located in series in the primary and secondary main metering air lines. These check valves will prevent any liquid fuel from entering the altitude compensator housing. The altitude compensator is attached to the front of the heater air intake duct. The fresh air inlet to the compensator is connected at the bottom of the air cleaner housing. The one-way check valves (if equipped) are located in the air lines near the carburetor.