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2.
Now close the needle-valve until the engine speeds
up to "two-cycle"operation and allow it to run for
about 10 seconds, then reopen the needle-valve to
bring the engine back to "four-cycle"operation and
run it for another 10 seconds. Repeat this procedure
until the fuel tank is empty.
Re-start and adjust the needle-valve so that the
3.
engine just breaks into "two-cycle" from "four-cycle"
operation, then make three or four flights, avoiding
successive "nose-up" flights.
Optimum needle setting (1)
Slowly advance the throttle to its fully open position,
then gradually close the needle-valve until the exhaust
note begins to change. (4-cycle to 2-cycle)
Needle-valve adjustment diagram
Practical best(optimum) needle-valve setting
6
Clear, high-pitched two-stroke
exhaust note
5
Intermittent, high-pitched
two-stroke note
superimposed
on low "four-stroke"
sound.
4
Disconnect battery
leads from glowplug at
about this point.
3
Exhaust note starts to change.
IDLING ADJUSTMENT CHART
Start the engine.
Disconnect the battery leads at mid speed.
Make sure that the throttle is
fully open.
Adjust the neede-valve.
˚
20-45
open from maximum r.p.m. setting.
Close the throttle gradually.
Set the idle speed
The position where the lowest possible
r.p.m. ,with steady running, is obtained.
Set the throttle opening by means
of the throttle trim on the transmitter so
that the lowest practical speed, without
risk of the engine stopping,is obtained.
Re-set the idle speed
at a little higher r.p.m.
Open the throttle fully.
Does the engine
Engine
regain full power?
stops.
Continue running at high speed
for 10 seconds.
Close the throttle.
Run at idling speed for 5 seconds.
Engine
Does the engine stop?
stops.
Apply full throttle.
Does the engine regain
Engine
full power immediately?
stops.
Refer to the next section.
OK
4.
During subsequent flights, the needle-valve can be
gradually closed to give more power. However, if
the engine shows signs of running too lean, the next
flight should be set richer. After a total of ten flights,
the engine should run continuously, on its optimum
needle-valve setting, without loss of power as it
warms up.
5.
After the completion of the running-in adjust the
carburetor at optimum setting referring to MIXTURE
CONTROL VALVE ADJUSTMENT section and
SUBSEQUENT READJUSTMENT section.
Optimum needle setting (2)
As the needle-valve is closed slowly and gradually, the
engine r.p.m. will increase and a continuous
high-pitched exhaust note, only, will be heard. Close
the needle-valve 10-15 degrees and wait for the
change of r.p.m. After the engine r.p.m. increases turn
the needle-valve another 10-15 degrees and wait for
the next change of r.p.m. As the speed of the engine
does
readjustment, small movements, with pauses between,
are necessary to arrive at the optimum setting.
7
Maximum rpm
setting("Lean").
1
STARTING
"Rich" needle-valve
setting when starting
the engine.
2
The engine may stop if
the battery leads are
disconnected from the
glowplug
engine is running rich.
Note: Although this is a two-stroke engine it fires like a four-stroke at these
rich needle-valve settings-i.e. ignition of the fuel charge takes place at
every fourth stroke of the piston instead of at every second stroke.
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. 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.
Note:
Mixture Control Valve adjustments should be
Yes.
made in steps of
checking the effect, on throttle response, of
each small adjustment.
REALIGNMENT OF MIXTURE CONTROL VALVE
In the course of making carburetor adjustments, it is
just possible that the Mixture Control Valve may be
inadvertently screwed in or out too far and thereby
moved beyond its effective adjustment range. Its basic
setting can be re-established as follows:
No.
Close the throttle rotor gradually from the fully opened
position until it is just fully closed. (Do not turn further.)
Then, screw in the Mixture Control Screw until it stops.
Now unscrew the Mixture Control Screw approx. 3/4
turn. This is the basic position.
Yes.
not
instantly
change
with
Note :
This diagram is for reference
purposes only.
Actual needle positions may
differ from those shown.
while
the
15-30˚ initially, carefully
SUBSEQUENT STARTING PROCEDURE
Once the optimum needle-valve setting has been
established the procedure for starting may be
simplified as follows.
1.
Open the needle-valve one half-turn (180 degrees)
from the optimum setting.
2.
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.
Note:
When re-starting the engine on the same day,
provided that atmospheric conditions have not
changed significantly, it may be practicable to
re-start the engine on its optimum(running) setting.
SUBSEQUENT READJUSTMENT
Once the engine has been run-in and the controls
properly set up, it should be unnecessary to alter the
needle-valve
mixture settings; except to make minor adjustments to
the Needle-Valve occasionally, to take account of
variations in climatic conditions. The use of a different
fuel, however, particularly one containing more, or
less, nitromethane and/or a different type or proportion
of lubricating oil, is likely to call for some readjustment
of the Needle-Valve. Remember that, as a safety
measure, it is advisable to increase the Needle-Valve
opening by an extra half-turn counter-clockwise, prior
to establishing a new setting. The same applies if the
silencer type is changed. A different silencer may alter
the exhaust pressure applied to the fuel feed and call
for a revised Needle-Valve setting. The use of a
different glowplug may also require compensating
carburetor readjustments.
CARE AND MAINTENANCE
Please pay attention to the matters described
below to ensure that your engine serves you well
in regard to performance, reliability and long life.
As previously mentioned, it is vitally important to
avoid operating the engine in conditions where dust,
disturbed by the propeller, may be deposited on the
engine and enter its working parts.
Remember to keep your fuel container closed to
prevent foreign matter from contaminating the fuel.
Install a fuel filter to prevent dirt and dust in the fuel
container from entering the fuel tank. O.S. Super
Filters (L) and (S) are available as optional extras.
Install an in-line fuel filter between the tank and
carburetor to prevent dirt and dust in the tank from
entering the carburetor.
Clean these filters periodically.
If these precautions are neglected, restriction of fuel flow
may cause the engine to cut out, or the fuel/air mixture
to become too lean causing the engine to overheat.
The use of modern high-performance alcohol based
model engine fuels, while promoting cooler running,
improved anti-detonation combustion and increased
power, have the disadvantage of causing corrosion
due to the acid by-products of combustion. The use
of nitromethane in the fuel can also contribute to the
problem.
Do not close the needlevalve and mixture control
valve too far as this will cause a lean setting and
over heating of the engine. This can, in turn, create
nitromethane oxide leading to internal rusting of the
engine. Always adjust the needlevalve slightly on the
rich side of peak rpm.
Do not leave unused fuel in the engine at the
conclusion of a day's flying. Accepted practice is to
cut off the fuel supply while the engine is still running
at full throttle, then expel as much fuel residue as
possible by turning the engine over 5-10 seconds
with the electric starter. Finally, inject some after-run
oil through the glowplug hole and turn the engine
over several times by hand.
When the engine is not to be used for some months
(for example, as between flying seasons), a
worthwhile precaution is to remove it from the
airframe and, after washing off the exterior with
alcohol (not gasoline nor kerosene), remove
carefully the carburetor, glow plug and all silicone
tubing and put them safely aside.
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