O.S. Engines 21RZ-R (P) - Manual (Page 15)

IF THE ENGINE FAILS TO START
Check the following:
Glowplug battery discharged or glowplug defunct.
Fuel not reaching carburetor.
◆
◆
◆ Engine flooded. Do not over-prime. (This could also
cause hydraulic lock and damage the engine on
application of the electric starter.) Remove glow-
plug, close needle-valve and apply starter to pump
out surplus fuel.
◆
◆
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 45~90˚. ◆
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
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˚.
FINAL ADJUSTMENT
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.
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