7. Incorrect air/fuel mixture.
8. Plugged carburetor jets.
9. Partially plugged fuel tank breather hose.
10. Faulty fuel pump.
11. Faulty starting circuit cutoff relay.
Incorrect Fast Idle Speed
A fast idle speed can be due to one of the follow-
ing problems:
1. Idle adjust screw incorrectly set.
2. Incorrect carburetor synchronization.
3. Stuck choke valve.
Poor Fuel Mileage and
Engine Performance
Poor fuel mileage and engine performance can be
caused by infrequent engine tune-ups. Check your
records against the recommended tune-up intervals
in Chapter Three. If your last tune-up was within
the specified service intervals, check for one or
more of the following problems:
1. Clogged air filter.
2. Clogged fuel system.
3. Loose, disconnected or damaged fuel and emis-
sion control vacuum hoses.
4. Ignition system malfunction.
Rich Fuel Mixture
A rich carburetor fuel mixture can be caused by
one or more of the following conditions:
1. Clogged or dirty air filter.
2. Worn or damaged fuel valve and seat.
3. Clogged air jets.
4. Incorrect float level (too high).
5. Flooded carburetor(s).
6. Damaged vacuum piston.
Lean Fuel Mixture
A lean carburetor fuel mixture can be caused by
one or more of the following conditions:
1. Clogged carburetor jet(s).
2. Clogged fuel filter.
3. Restricted fuel line.
4. Intake air leak.
5. Incorrect float level (too low).
6. Worn or damaged float valve.
7. Faulty throttle valve.
8. Faulty vacuum piston.
Engine Backfires
1. Lean fuel mixture.
2. Incorrect carburetor adjustment.
Engine Misfires During Acceleration
When there is a pause before the engine responds
to the throttle, the engine is misfiring. An engine
misfire can occur when starting from a dead stop or
at any speed. An engine misfire may be due to one
of the following:
1. Lean fuel mixture.
2. Faulty ignition coil secondary wires. Check for
cracking, hardening or bad connections.
3. Faulty vacuum hoses. Check for kinks, splits or
bad connections.
4. Vacuum leaks at the carburetor(s) and/or intake
manifold(s).
5. Fouled spark plug(s).
6. Low engine compression, especially at one cyl-
inder only. Check engine compression as described
in Chapter Three. Low compression can be caused
by worn engine components.
7. Faulty fuel pump.
CARBURETOR HEATER
Whenever there is a problem with the carburetor
heater system, follow the carburetor heater trouble-
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CHAPTER TWO
7
Bent terminal