O.S. Engines 21VZ-B - Manual (Page 8)

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It is vitally important to set the
throttle at the correct position
before starting the engine. If
the engine is allowed to run
with the throttle too far open
under ''no load'' conditions (i.e. with the driving
wheels not in contact with the ground) it will rapidly
over-heat and may be seriously damaged.
Attention:
When the engine starts, first allow it to operate in
short runs at the very rich starting settings, with the
glowplug battery still connected and the driving
wheels clear of the ground.
The rich mixture will, under these conditions,
provide adequate lubrication and cooling, indicated
by profuse smoke from the exhaust.
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.
To stop the engine, close the throttle to idling
speed, then shut it off completely with the trim lever
on the transmitter. To cut off the fuel supply, pinch
the fuel delivery line to the carburetor.
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 another full tank of fuel.
Repeat this procedure until 5 more tanks of fuel
have been consumed, during which time the throttle
may be opened for brief bursts of increased power.
Needle
The position of the needle-valve when starting
the engine.
Close the needle-valve approx.
30˚ after running the vehicle for
one full tank of fuel.
Repeat this procedure several times. •
•
•
If the engine should need to be disassembled (e.g.
for cleaning or minor parts replacement) it is
advisable to return the Needle-Valve to the original
rich, starting setting and check whether further
running-in time is required before the car is raced
again. In the event of any major working parts(e,g,
piston/cylinder liner assembly) being replaced, the
complete running-in should be repeated.
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 glowplug, close
needle-valve and apply star-
ter 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˚.
FINAL ADJUSTMENT
Having established the optimum Needle-Valve
setting, check the Mixture Control Valve setting as
follows.