FUEL SYSTEM
Float System
The float system is designed to maintain a constant height of
gasoline during operation. When the fuel flowing from the fuel
pump into the float chamber through the needle valve reaches
the constant fuel level, the floats rise. When the buoyancy of
the float and the fuel pressure of the fuel pump balance, the
needle valve seals the orifice in the needle seat, preventing
further fuel delivery, and the level of fuel in the bowl remains
relatively constant.
The fuel level in the bowl assists in controlling the amount of
fuel in the fuel mixture. Too high a level allows more fuel than
necessary to leave the nozzle, enriching the mixture. Too low a
level results in a leaner mixture, since not enough fuel leaves
the nozzle. Therefore, the predetermined fuel level should not
be changed arbitrarily.
Pilot Jet
From idling to low speeds, the fuel supply is metered by the
pilot
jet. There are several air bleed openings in the sides of the
pilot jet which reduce the fuel to mist. The number stamped on
the jet is an indication of the amount of fuel in cc’s which
passes through the jet during a one minute interval under a
given set of conditions.
Air Mixture Screw
The pilot mixture screw controls the fuel mixture from idle to
low speeds. The tapered tip of the mixture screw projects into
the fuel mixture passage leading to the pilot jet air bleeds. By
turning the screw in or out, the cross sectional area of the air
passage is varied, in turn varying the pilot jet air supply and
changing the mixture ratio.
The air screw is calibrated at the factory to meet EPA /
CARB regulations for air quality standards. Cleaning of
the pilot circuit must be performed by a certified repair
shop to ensure air quality standards are not exceeded.
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