Carburetor: Description and Operation

Fig. 1 Exploded view of Carter BBD Series 2 barrel carburetor:

The Carter Model BBD two barrel carburetor, Fig. 1, incorporates three light weight aluminum assemblies, the air horn, main body and throttle body. The air horn contains the choke valve, mechanical linkage for the accelerator pump and metering rods and bowl vent mechanism. The main body contains the fuel bowl, accelerator pump, vacuum piston and metering rod, venturi assembly and solenoid, if equipped. The throttle body contains the throttle valves and levers, choke housing, choke vacuum diaphragm and idle mixture screws.
The carburetor is of the feedback type, whose stepper motor has two tapered metering pins. Each metering pin is moved in and out of the carburetor to achieve the proper air/fuel ratio.