O.S. Engines 21VG-PX - Manual (Page 13)

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Next, disconnect the glowplug battery and try
running the car on the track. If the engine stalls,
open the throttle fractionally, but try to keep the
engine running as rich as possible: if it stops
because of being excessively over-rich, close the
Needle-Valve 30˚ and try again.
Run the car on the track until one tank of fuel has been
consumed, then close the Needle-Valve 30˚ and run
the car for 1 full tanks of fuel. Repeat this procedure
until approx. 2 liter of fuel have been consumed,
during which time the throttle may be opened for brief
bursts of increased power. If the engine stops at
medium speeds, close the Mixture Screw 45˚.
Needle
The position of the needle-valve
when starting the engine.
Close the needle-valve approx.
30˚ after running the vehicle for
1 full tanks of fuel.
Repeat this procedure until
approx. 1 liter of fuel have
been consumed.
Note:
In the event of any major working parts (e.g.
piston/cylinder liner assembly) being replaced or the
fuel being changed, especially to high nitro fuel, the
complete running-in should be repeated.
Warning!
Do not touch rotating parts, engine and silencer
when stopping the engine as they become very hot,
and contact with them may result in a serious burn.
To stop the engine, close the throttle to idle speed
and shut it off completely with the trim lever on the
transmitter then cut off the fuel supply by pinching
the fuel delivery tube to the carburetor.
Fuel
How to stop the engine
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FINAL ADJUSTMENT
Metering
Needle
Open Close Close Open
Needle Valve Metering Needle
More fuel Less fuel More fuel Less fuel
Final adjustment should be carried out only
after the running-in has been completed.
Needle Valve
Mixture Control
Screw
Adjust high RPM running.
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 .