O.S. Engines 160FX Ring - Manual (Page 14)

MIXTURE CONTROL VALVE ADJUSTMENT
With the engine running, close the throttle and allow it to idle
for about five seconds, then open the throttle fully. If, at this
point, the engine is slow to pick up and produces an excess of
exhaust smoke, the mixture is too rich. Correct this condition
by turning the Mixture Control Screw clockwise 15-30˚. If the
mixture is excessively rich, engine rpm will become unstable:
opening the throttle will produce a great deal of smoke and
rpm may drop suddenly or the engine may stop. This
condition may also be initiated by excessively prolonged
idling.
If,on the other hand, the mixture is too lean, this will be
indicated by a marked lack of exhaust smoke and a tendency
for the engine to cut out when the throttle is opened. In this
case, turn the Mixture Control Screw counter-clockwise 90˚to
positively enrich the idle mixture, then turn the screw
clockwise gradually until the engine regains full power cleanly
when the throttle is reopened.
Carry out adjustments patiently until the engine responds
quickly and positively to the throttle control.
Note: Mixture Control Valve adjustments should be made
in steps of 15-30˚ initially, carefully checking the
effect, on throttle response, of each small
adjustment.
REALIGNMENT OF MIXTURE CONTROL VALVE
In the course of making carburettor adjustments, it is just pos-
sible that the Mixture Control Valve may be inadvertently
screwed in or out too far and thereby moved beyond its effec-
tive adjustment range.
Its basic setting can be re-established as follows:
Close the throttle rotor gradually from the fully opened posi-
tion until it is just fully closed. (Do not turn further.) Then,
screw in the Mixture Control Screw until it stops. Now un-
screw the Mixture Control Screw approx. 2 turns.
2
1
SUBSEQUENT STARTING PROCEDURE
Once the optimum needle-valve setting has been established
(see page 19, Needle-valve adjustment diagram) the
procedure for starting may be simplified as follows.
Open the needle-valve one half-turn (180
°
) from the
optimum setting.
Set the throttle one-quarter open from the fully closed
position, energize the glowplug and apply the electric
starter. When the engine starts, re-open the throttle and re-
adjust the needle-valve to the optimum setting.
When re-starting the engine on the same day, provided
that atmospheric conditions have not changed signifi-
cantly, it may be practicable to re-start the engine on its
optimum(running) setting.
Note:
1.
2.
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