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TM 10-3930-653-14&P
4-5-2. TROUBLE DIAGNOSES AND CORRECTIONS
In
the
following
table,
the
symptoms
and
causes
of
carburetor problems and remedies
for them are listed to facilitate
quick repairs. There are various
causes of engine malfunctions. It
sometimes
happens
that
a
carburetor only appears to have
some problems, when actually the
electric
system
is
at
fault.
Therefore, whenever the engine is
malfunctioning, the electric system
should be checked first before
adjusting the carburetor.
Condition
Probable cause
Corrective action
Overflow
Dirt accumulated on needle valve.
Clean needle valve.
Fuel pump pressure too high.
Repair pump.
Needle valve improperly seated.
Replace.
Excessive fuel
Fuel overflow.
See above item.
consumption
Each main jet, slow jet too large.
Replace.
Each main air bleed clogged.
Clean.
Choke valve does not fully open.
Adjust.
Outlet valve seat of accelerator pump improper.
Lap.
Linked opening of secondary throttle valve too early
Adjust.
Power shortage
Each main jet clogged.
Clean.
Each throttle valve does not fully open.
Adjust.
Idling adjustment incorrect.
Repair.
Fuel strainer clogged.
Clean.
Vacuum jet clogged.
Clean.
Air cleaner clogged.
Clean.
Diaphragm damaged.
Replace.
Power valve operated improperly.
Adjust.
Improper idling
Slow jet clogged.
Clean.
Each throttle valve does not close.
Adjust.
Each throttle valve shaft worn.
Replace.
Packing between manifold/carburetor damaged.
Replace packing.
Manifold/carburetor tightening improper.
Correct tightening.
Fuel overflow.
See the first item.
4-62
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