McCulloch 250 - MAIN FUEL ADJUSTMENT NEEDLE

Main Fuel Adjustment Needle
1. Start and warm up the engine thoroughly.
2. Start the saw into a cut and check to see that under load, it runs
smoothly and evenly.
3. Open (turn counterclockwise) the main fuel adjustment needle
about 1/ 16 turn, and with the slightly richer mixture, again check
the engine running under load.
4. Repeat this adjustment and check, in very gradual steps until
the engine begins to develop rough running under load.
5. Close the needle (turn clockwise) just enough to eliminate the
roughness. 1m
NOTE
After final adjustment, make sure that when the
saw is pulled from the cut, with the engine under
no load, it has the characteristic roughness of a
rich carburetor setting.
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If the main fuel adjustment needle is set while the
saw is not under load, the mixture may be too lean.
While the exhaust may be sharp and barking and
sound powerful, costly damage can be done to the
engine by the lean setting through overheating and
lack of lubrication. It is much better to run the
engine with a mixture slightly too rich, than one with
FUEL TANK FILTER
a mixture slightly too lean. Be sure therefore, that
final adjustment of the main needle is made only
The fuel tank contains a fuel pick-up tube which has a self-filter
for full load conditions.
in the open end of the bell on the tube. The filter will prevent
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