Rebuilding Procedures (Zenith 63AW)
Fuel supply system (Zenith 63AW)
High Speed (Main Metering) System (Zenith 63AW)
Accelerating System (Zenith 63AW)
The carb ID number is on this tag which is rivited to the top of the carburetor. You will need the inner number, which will be 4-5 digits with a letter at the end.
If this tag is missing, you will have a hole through the top of the lid, it is not removable.
The 63-series carburetors are of the single barrel updraft design with double venturi and twin floats. The use of the twin floats together with a fuel bowl that hugs the center line of the carburetor permits operation at extreme angles without flooding or starving the engine. These carburetors are of the “sealed” and “balanced” type since all air for fuel bowl ventilation and idle operation must enter through the air cleaner.
The power jet and accelerating pump systems are operated by engine manifold vacuum. Some models are equipped with semi-automatic choke, others will full manual choke system. The fuel system includes the fuel inlet fitting, fuel valve (needle and seat), twin floats and the float chamber.
The idle system consists of the idle discharge port, vacuum passage, idle adjusting needle, idle air passage, idle jet, idle well, idle fuel restriction and idle feed holes. The high speed (main metering) system consissts of the main venturi, secondary (small) venturi, discharge jet, main jet fuel passage, well vent jet (high speed air bleed), metering well, main jet and main jet adjustment.
The power jet system includes the power jet valve, pump check valve, power jet, discharge jet passage, vacuum piston and a vacuum passage that connects the vacuum piston with the intake manifold. The accelerating pump system consists of a power and accelerating jet, pump check valve, pump piston, spring, vacuum piston and a vacuum passage that connects the vacuum piston with intake manifold vacuum. The choke system includes a choke plate (valve) mounted on a shaft in the air intake and operated by an external lever. Some units include a spring loaded poppet valve mounted within the choke plate.