O.S. Engines 15LD-X - Manual (Page 17)

With the optimum mixture control position, light
smoke is visible during high speed running,and the
engine revolutions increase smoothly during
acceleration. Remember that, if the engine is
operated with the fuel/air mixture slightly too lean, it
will overheat and run unevenly. As with all engines,
it is advisable to set both needle-valve and mixture
control screw very slightly on the rich side of the best
rpm setting, as a safety measure.
If the engine runs too fast with the throttle closed,
the throttle stop screw should be turned counter-
clockwise to allow the throttle opening to be
reduced.
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•
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Finally, beyond the nominal break-in period, a slight
readjustment toward a leaner needle setting may be
required to maintain performance.
CARBURETOR CLEANLINESS
The correct functioning of the carburetor depends on
its small fuel orifices remaining clear.
BALL LINK AND SLIDE VALVE EXTENSION
It is seldom necessary to separate the slide-valve
extension from the slide-valve itself. For cleaning,
withdraw this complete sub-assembly from the
carburetor body after removing the slide-valve guide
screw. Then wash with methanol or glow-fuel.
(Note: take care not to lose the guide screw;it is a
special one.)
When it is necessary to adjust the ball-link position,
loosen the ball-link retaining screw with a 1.5mm
hexagon key, re-align the ball-link and re-tughten the
screw firmly.
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