O.S. Engines 15CV-X - Manual (Page 18)

In this case, turn the Mixture Control Valve
clockwise 45~90˚. If, on the other hand, the engine
tends to speed up momentarily and then cut out
abruptly when the throttle is opened,the idling
mixture is too lean. Correct this by turning the
Mixture Control Valve counter-clockwise 45~90˚.
Warning!
NOTE:
Mixture Control Valve adjustment should be made
in steps of not more than 45~90˚, carefully
checking the effect,on throttle response, of each
small adjustment.
Carry out adjustments patiently, under actual
running conditions, until the engine responds
quickly and positively to the throttle control.
Mixture adjustments (whether via the Mixture
Control Valve, or the Needle-Valve) cannot be
made accurately under 'no-load' conditions,
which, in any case, are not advised, since such
operation carries the risk of seriously damaging
the engine through over-revving and overheating.
•
•
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.
•
•
• 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.
(See Care and Maintenance section on Page19.)
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