7-6-2021
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Most of the time
the problem of erratic erratic running is caused by debris in
the carburetor. Many times we receive engines back only to find
foreign matter has been introduced into the fuel passage of
the carburetor. |
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This is an actual
engine that was returned to us because it was overheating and
running erratically for a few minutes before it would die. After
removing the main needle and receptacle this is what we found,
honest. This was so apparent we couldn't believe it either,
that's why we took the picture. This is either a sliver of fuel
line apparently when it is pushed over the brass tubing on the
fuel tank or some silicone sealant. If you use silicone sealant
don't use it on nipples or other parts of the carburetors. Naturally
the customer sent the engine back for warranty, but how can
this be consider this the factory's fault? |
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Anytime debris is
in a fuel passage it moves around causing the mixture to change
as it plugs and unplugs the fuel flow, hence rich, lean,
correct settings, but no constant setting. |
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On other types
of carburetor designs, like this K&B mixture disc, you
must check inside the spray bar as many times something is
plugging up the metering slot that controls the fuel flow
for idle and midrange. Symptoms are not being able to obtain
idle settings, not getting a rich enough high speed setting,
and erratic settings as described above.
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Another
culprit of erratic running is Muffler Pressure.
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We found that sometimes
the muffler pressure nipple can become plugged up with oil residue
from the exhaust. When this happens the fuel tank receives pressure
then not so the result is the fuel mixture is never the same.
One time the fuel is being supplied under pressure then not
or even to the point no fuel because no vent or pressure is
present in the tank. Try running the engine with the pressure
nipple disconnected. If the engine performs differently this
may be the problem. Try changing brand fuels or replacing the
nipple with one that is designed with a stand off available
from MECOA. |
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