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STARTING CHOKE OPERATION
Starting an engine with the “HL” Carburetor involves the same methods that are used in a conventional float
feed carburetor. However, since a diaphragm carburetor does not have the advantage of a great reservoir of
fuel upon which to operate, the technique changes somewhat.
When starting a cold engine, place the choke shutter in the closed position and throttle shutter in a cracked or
open position. Several pulls on the starter may be needed to raise the fuel pressure to the required amount.
As the engine is pulled through with the choke in closed position, engine suction will be transmitted to the
diaphragm fuel chamber through both primary and secondary idle discharge parts as well as the main fuel
discharge part, 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, by
forcing inlet needle off its seat contact, then into the fuel chamber side of main diaphragm, up through the idle
and main fuel supply orifices and channels, and out the discharge parts to the engine.
In starting an engine that has been idle and not running for more than an hour, it will be necessary to operate
and manoeuvre the choking mechanism for approximately three (3) to ten (10) seconds depending on how
cold the engine has become. The length of time spent warming the engine is only necessary to the extent that
the engine can be made to idle, accelerate and run satisfactorily under wide open throttle conditions.
IDLING OPERATION
When engine is idling, throttle shutter is in a partially cracked position. 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, by forcing inlet
needle off its seat contact, and filling the fuel chamber side of main diaphragm. The fuel is then drawn up
through idle fuel adjustment orifice and delivered to the engine through primary idle discharge port.
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