O.S. Engines 65AX - Manual (Page 16)

30
IDLING ADJUSTMENT CHAR
T
Start the engine.
Make sure that the throttle is fully open.
Adjust the needle-valve.
Close the throttle gradually.
Set the idle speed
Open the throttle fully.
Does the engine regain full power?
Continue running at high spee
d
for 10 seconds.
Close the throttle
.
Run at idle speed for 5 seconds.
Does the engine stop?
Apply full throttle.
Does the engine
regain full power immediately?
OK
Refer to the next section. Re-set the idle speed at a little higher r.p.m
.
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The position where the lowest p
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ss
ib
le
r
.p
.m
.
,w
it
h
s
te
a
d
y
running, is obtained. 20-45 open from maximum r.p.m. setting.
Yes
.
No
.
Yes.
Engine stops. Engine stops.
Disconnect the battery leads at mid speed.
Engine stops.
31
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
degrees. 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.
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.
In this case, turn the Mixture Control Screw
counter-clockwise 90 degrees 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.