STARTING CHOKE OPERATION
Starting an engine with the “HU” Carburetor involves the same methods that are used in a conventional float feed
carburetor
When starting a cold engine, place the shutter blade in the closed position and throttle shutter in a cracked or
open position. As the engine is cranked, engine suction will be transmitted to the diaphragm fuel chamber
through both primary and secondary idle discharge ports as well as the main fuel discharge port, creating a low-
pressure area on the fuel side of the main diaphragm. Atmospheric air pressure on the opposite side will force
the main diaphragm upward causing the diaphragm button to depress the inlet control lever, overcoming inlet
tension spring pressure, permitting fuel to enter through the inlet seat, then into the fuel chamber side of main
diaphragm, up through the idle and high speed fuel supply orifices and channels, and out the discharge ports to
the engine.
IDLING OPERATION
When engine is idling, throttle shutter is partially cracked. Engine suction is transmitted through the primary idle
fuel discharge port to the fuel chamber side
of main diaphragm via the idle fuel supply channel. Again, the main
diaphragm is forced upward by atmospheric pressure, depressing the inlet control lever overcoming inlet tension
spring pressure and permitting fuel to enter through inlet seat, and filling the fuel chamber. Fuel is then drawn up
through idle mixture screw orifice and delivered to the engine through primary idle discharge port.
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