O.S. Engines 18TZ(S)-T - Manual (Page 22)

FINAL ADJUSTMENT
Run the vehicle (with throttle fully open) over
the longest available straight course, in order
to observe the model's speed. Next return
the car to the starting point, close the Needle-
Valve 30° and repeat the run, taking note of
the improvement in performance. Continue
with further runs, gradually reducing the
Needle-Valve setting and aiming to achieve
the highest straight-line speed. Remember,
however, that, if the Needle-Valve is shut
down too far, the engine will overheat and,
accompanied by visibly diminished exhaust
smoke, the model will lose speed. At this
point, throttle down immediately, stop the
vehicle and reopen the Needle-Valve 30°.
Having established the optimum Needle-
Valve setting, check the Mixture Control
Valve setting as follows.
With the engine running, close the throttle
and allow it to idle for about five seconds,
then reopen the throttle fully. If, at this point,
the engine puffs out an excessive amount of
smoke and the vehicle does not accelerate
smoothly and rapidly, it is probable that the
idling mixture is too rich,
In this case, turn the Mixture Control Valve in
case of the 11 L and the Metering Needle in
case of the 11 K clockwise 45 degrees. 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 in case of the 11L and the
Metering Needle in case of the 11K counter-
clockwise 45 degrees.
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