Maintenance
2.37
General Troubleshooting
The following information is provided to help you identify possible causes for conditions/symptoms listed. Always
verify tune-up adjustments and all related basic maintenance has been performed. These items are randomly
listed, and are not necessarily in order of most common occurrence.
Lean Condition
Symptoms: Hard starting; bogging; hesitation; backfire; surging; detonation; engine noise; low power; spark plug
light colored or eroded; engine runs hot; high or unstable idle; piston failure; application of choke improves condi-
tion. Stalling (may restart immediately or soon afterward); high speed surging; high speed or sharp turns makes
condition worse (may hesitate or stall only in turns). Too lean at full throttle, turning high speed adjuster screw
out improves condition or has no affect.
S Fuel level low or fuel contaminated
S Restricted fuel filter, fuel pump, or fuel shut-off valve
S W ater in fuel valve, pump, or lines
S Water present in fuel system
S W ater in carb fuel chambers between diaphragm, jet block and jets
S Kinked or restricted fuel tank vent or fuel lines
S Fuel tank inlet check valve damaged, faulty, or improperly installed
S Vent lines kinked
S Air leaks at fuel pickup connections or lines between pump and tank
S Fuel pickup tube disconnected or loose in tank
S Fuel pump impulse line pinched, kinked, restricted with oil or water, or leaking
S Carburetors dirty; main pilot or bypass orifices restricted; fuel inlet screen plugged
S Carburetor synchronization incorrect
S W ater separator full or restricted
S W ater in fuel tank
S High or low speed screws adjusted incorrectly; jets too small or restricted
S Fuel pump diaphragm or check valve damaged
S Fuel filter restricted
S Carburetor jetting incorrect
S Fuel tank pickup screen plugged
S Air leaks in engine intake tract (carburetor base gaskets, reed gaskets, synchronizing plugs, etc.)
S Carburetor inlet needle or control lever arm stuck or adjusted incorrectly
S Fuel line “T” restricted
S Inlet needle valve restricted or size too small
S Air leaks at cylinder base, crankcase drain plugs, fuel pump impulse line or fitting, carburetor
base gaskets, reed cage gaskets, crankshaft end seals, crankcase mating surfaces
Poor Performance
S Rich or lean fuel condition.
S Jet pump impeller damage, pump cavitation/ventilation.
S Ignition timing incorrect, weak or intermittent spark on one or more cylinders, low compression
S RPM is limited or timing retarded due to low fuel or overheating (where applicable)
S Crankshaft out of index due to hydrolock by fuel or water (see hydrolock troubleshooting this sec-
tion) Low cylinder compression, damaged flywheel.
S Fuel lines connected improperly
S Ignition timing retarded or RPM limited due to overheat or low fuel (where applicable)
S W ater leak into exhaust system (i.e. exhaust pipe to manifold; exhaust manifold to cylinders; etc.)
S Exhaust hose delamination present.
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