62
FUEL SYSTEM
Read all of SAFETY and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
Figure 4 Fuel Tank
Late Production Fuel Tank
Late production tanks can be identified by the sending
unit and the siphon tube as shown in (Figure 2).
Late production fuel tanks are designed to allow for fuel
expansion and do NOT require space below bottom of
filler neck.
Figure 5 Fuel Tank
CARBURETOR OPERATION
The carburetor consists of four different systems:
• Float System
• Pilot Jet System
• Main Jet System
• Choke System
Float System
The float chamber is located on the underside of the car-
buretor. The correct fuel level is maintained by means of
the float and needle valve.
As the fuel flows from the fuel pump, it must pass through
the needle valve and into the float chamber. As the fuel
enters the float chamber, the float starts to rise against
the needle valve. When the buoyancy of the float exceeds
the fuel pressure on the needle valve, the float closes the
needle valve. The float maintains the correct fuel level
within the float chamber and it is not adjustable. As fuel is
consumed from the float chamber, the float drops which
allows the needle valve to admit additional fuel.
Pilot Jet System
The pilot jet system function is to deliver fuel to the engine
during low speed operation. The fuel flow is determined
by the pilot jet size and the setting of the pilot screw.
Main Jet System
The main jet system function is to deliver fuel to the
engine during acceleration and heavy load conditions.
Fuel flow is determined by the main jet size. Air is mixed
with fuel that passes through the bleed opening in the
main nozzle. This mixture passes into the carburetor ven-
turi as atomized air/fuel is mixed with intake air and deliv-
ered to the engine.
Choke System
The choke functions to make initial starting of the engine
easier in cold weather conditions. The choke plate
restricts the air flow into the carburetor which enriches the
air/fuel ratio.
Carburetor Service
Be sure that the ignition system is functioning correctly
before determining that servicing the carburetor is
required. Refer to the ELECTRICAL section for ignition
system information.
Choke Operation
Pull the choke knob (10) out to operate the choke (Figure
6). Check that the cable operates smoothly and that the
cable returns when the knob is released. The motion
should be smooth throughout the operating range. If there
is any binding or sharp bends, the choke cable assembly
must be replaced.
Do not attempt to lubricate the choke cable. Lubricant
tends to retain dirt on the moving parts which will cause
premature deterioration of the cable.
To decrease the risk of an ignition spark which
could ignite gasoline from the fuel system and
result in personal injury, the negative (-) bat-
tery cable must be removed from battery (refer
to SAFETY section).
1MR
GQ
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