RUNNING-IN ("Breaking-in")
ADJUSTMENT
2. High Speed needle-valve:
approx. two turns open from the fully closed
position. (Note: If a different muffler is used, this
setting may require readjustment)
Idle Mixture Control Screw:
at basic position when the engine leaves the factory.
one turn open from the fully closed position.
Medium Speed needle-valve:
4. Checking the rotating direction of the starter
Make sure that the starter rotates to the direction
shown in the sketch. If the direction is reverse,
reverse the leads on battery.
3. Preparation of the starter
Install the starting shaft to the starter securely.
Improper installation will allow the shaft to swing
creating a dangerous situation.
5. Inserting the starter shaft
Insert the starting shaft into the shaft cup securely.
6. Priming
Check the movement of all the controls after
switching on both the transmitter and the receiver.
Then, fully open the throttle valve without heating
the plug. Turn the engine with an electric starter
until the fuel comes into the carburetor inlet.
Stopping the engine
Fully pull down the throttle trim on the transmitter.
Starting
Connect the battery to the glowplug and start the
engine by applying the starter. When started, switch
off the starter and withdraw the starting shaft after
making sure the rotation of the starter shaft stops.
Preparation of starting
7.
8.
9.
Hold the rotor head by hand so that rotor cannot rotate
when the engine is Started. Also, steady the model
with a foot on the landing gear skid.
Make sure that the transmitter throttle stick is at the
fully closed position and the throttle trim at center
position, and make sure that idle-up switch on the
transmitter is off.
In case the engine does not stop.
Hold the rotor head, and pinch the fuel line to stop the
fuel supply. If it still does not stop, pull off the fuel line
from the carburetor. It is necessary to readjust the
throttle linkage so that the carburetor rotor is fully
closed when the throttle stick and throttle trim on the
transmitter are fully pulled Down.
NOTE:
If the throttle response is poor or the engine stops
due to a temporarily over-rich mixture immediately
after the engine is started, pinch the fuel line for
one or two seconds until the engine r.p.m.
increase and the engine runs steadily.
All internal-combustion engines benefit, to some
degree, from extra care when they are run for the first
few times known as running-in or breaking-in.
This allows the working parts to mate together under
load at operating temperature.
However, because O.S. engines are made with the aid
of the finest modern precision machinely and from the
best and most suitable materrials, only a very short
and simple running-in procedure is required and can
be carried out with the engine installed in the model.
Main needle is set two turns open from fully closed
position and the medium speed needle is set one
turn open from fully closed position when the engine
leaves the factory.
It is expected with these needle settings the engine
may run rich. During running-in, hover the model
making sure the engine runs rich.
Also, during running-in since the mixture is rich, you
may feel uneven engine rpm and more fuel
consumption.
In the next section, needle adjustments to optimum
position from running-in position are explained.
Be sure to run the engine a little on the rich side so
that if will have a long life expectancy.
Please observe the following before beginning to
make any adjustment.
The general course of adjustment procedure is
shown in the ADJUSTING CHART and is correct
for a fuel containing 20% lubricant and 15-30%
nitromethane.
Bear in mind that fuels containing relatively large
percentages of power-boosting nitromethane operate
at richer mixture settings than are needed for mild
fuels and will, therefore, require the High-Speed
Needle Valve to be readjusted accordingly. The type
and percentage of lubricant used is also a factor here,
as noted later in these instructions.
This carburetor is not equipped with a throttle
stop screw. Instead, idle speed is adjusted by
means of the throttle trim lever on the transmitter.
High-Speed Needle Valve.
Turn this approximately 30 degrees (3 to 4 clicks) at a
time, when making initial adjustments; then in steps
of approximately 15 degrees (1 to 2 clicks) when
making final adjustments.
Medium-Speed Needle Valve.
Turn approximately 30 degrees (3 to 4 clicks) at a time.
Idle Mixture Control Screw.
Turn approximately 5 degrees at a time. It turns
approximately 90 degrees both sides from the center.
Turn left to enrich the idle mixture and turn right to
lean the idle mixture.
As a safety measure, first check the transmitter
controls, including the throttle stick and trim lever
positions, and hold the main rotor securely before
starting the engine.
Warm the engine by allowing it to idle for about 30
seconds. If the engine stops, advance the throttle
trim lever slightly to increase the idle rpm.
Then open the throttle sufficiently to 'float' the model
above the ground. lf, at this time, 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 5 degrees. lf the mixture is extremely
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.
ADJUSTMENT PROCEDURE
1.
This condition may also be initiated by an excessively
prolonged warming-up period. lf, on the other hand,
the mixture is too Iean, this wiIl be indicated by a
marked lack of exhaust smoke and a tendency for the
engine to cut out when the throttle is opened. ln this
case, turn the Mixture Control Screw counter-clockwise
5 degrees to enrich the mixture.
2.
Throttle Opening
Fully Closed
1/3
2/3
Fully Open
Fuel Flow
Maximum
Minimum
Adjustment range of Idle Mixture
Control Screw
Adjustment range of Medium
Speed Needle Valve
Needle Valve too
far open
Needle Valve too
far closed
High Speed Needle
Valve Setting varies
according to the curve.
Now re-check hovering performance It may be found
that (with the High-Speed Needle Valve now set for
optimum full-throttle performance) hovering will
reveal symptoms of slightly lean running at medium
speeds. DO NOT touch the High-Speed Needle Valve.
3.
4. Having now found the optimum setting for the
High-Speed Needle Valve, re-check the engine's
idle performance, fine tuning the Idle Mixture Control
Screw, if necessary, to perfect the idle.
5.
It is at this point that the Medium Speed Needle
Valve, previously set one and half turns open, may
be brought into operation. Open the Medium Speed
Needle Valve 30 degrees, or 3-4 clicks, then fine
tune until the optimum hovering performance is
obtained. If on the other hand, hovering reveals rich
running, close the Medium Speed Needle Valve
gradually until the optimum hovering performance is
obtained.
SUBSEQUENT READJUSTMENTS
CARBURETOR CLEANLINESS
Remove this with
an 8mm wrench
Dirt and foreign matter
mostly accumulate here
The correct functioning of the carburetor depends on
its small fuel orifices remaining clear. The minute
particles of foreign matter that are present in any fuel
can easily partially obstruct these orifices and upset
mixture strength so that engine performance becomes
erratic and unreliable. It is recommended that fuel is
passed through a filter when the tank is filled and that
a good in-line filter is installed between the fuel tank
and carburetor and, furthermore, that this filter is
frequently cleaned to remove foreign matter that
accumulates on the filter screen. Finally, occasionally
remove the needle-valve holder from the carburetor as
shown in Picture and extract any remaining foreign
matter that may have lodged in the location shown in
Picture below.
Having provisionally set the idle mixture, the next
step is to adjust the mixture for hovering flight.
Hover the model and actuate the throttle to observe
response over the medium speed range.
lf the engine smokes excessiveIy and throttle response is
poor, the mixture is too rich ; in which case, land the
model and turn the High-Speed Needle Valve clockwise.
Do not close the High-Speed NeedIe Valve more than
the recommended initial adjustment (3 to 4 clicks) at a
time, keeping it a little on the rich side at this stage.
DO NOT touch the Medium Speed Needle Valve.
lf, on the other hand, hovering is not stable and response
to the throttIe is over-sensitive, or if the engine tends to
overheat, this indicates that the mixture is too lean and
should be corrected by turning the High-Speed Needle
Valve counter-clockwise.
After about 10 seconds of idling, open the throttle to
'float' the model. lf the transition is smooth, the idle
mixture is O.K. If the symptoms of either rich or Iean
running are observed, readjust the Idle Mixture
Control Screw accordingly.
NOTE: With this carburetor, neither the Idle
Mixture Control Screw adjustment, nor the Medium
Speed Needle Valve adjustment will have any
effect on mixture strength when the throttle is fully
(or almost fully) open.
When satisfactory hovering flight has been
achieved, land the modeI again and re-check the
engine's idle qualities.
Now adjust the High-Speed Needle Valve to achieve
the best performance when the model is flying at full
throttle. lf, at full throttle, acceleration is poor, the
exhaust unduly smoky and the model fails to reach
expected straight line speed, the mixture is too rich
and the High-Speed Needle Valve setting will need
to be reduced.
lf, however, after smoothly acceIerating to satisfactory
high-speed straight and level flight, power is lost
when the model is puIled up into a climb, the mixture
is too lean. ln this case, land the model immediately
and readjust thw High-Speed Needle Valve to a
richer setting.
Once the engine has been run-in and the carburetor
controls properly set up, it should be unnecessary to
alter the mixture settings, except to make minor
changes to the Main (High-Speed) Needle Valve
occasionally, to take account of differences in climatic
condisitions.
However, as previously mentioned, the use of a
different fuel, particularly one containing more, or less,
nitromethane and / or a different type or proportion of
lubricating oil, is likely to call for some modification to
the High-Speed Needle-Valve adjustment.
As a safety measure, it is advisable to increase the
High-Speed Needle Valve setting by an extra half-turn
counter-clockwise, prior to establishing the 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, or changes to the
main rotor and its pitch angles may also require
compensating carburetor readjustments.
