26
Adjusting the mixture control valve
If the engine hesitates, puffing
out a good deal of smoke, before
picking up to full speed, it is
probable that the idle mixture is
too rich.
1.
Mixture Control Valve
Screwdriver
Turn 30
In this case, it will be necessary
to turn the Mixture Control Valve
clockwise to lean the mixture.
About 1/12 turn (30 ) should be sufficient.
Alternatively, if the engine stops
or is slow to pick up speed,
without smoking or a strong
exhaust note, it is probable that
the idle mixture is too lean.
2.
Turn 30
In this case, it will be necessary
to turn the Mixture Control Valve
counter-clockwise approximately
1/12 turn (30 ) .
Thirdly, if the rpm increase but the engine appears to run
with reduced power, it is probable that one of the cylinders
has ceased firing. You may detect this by the difference in
exhaust note and rpm compared with previous full-throttle
running. The cutting out of the cylinder may be caused by
the idle speed being set too low or the idle mixture being
too rich.
3.
In the case of the idle speed being too low, re-set the idle
position a little higher by means of the throttle trim on the
transmitter. In the case of the idle mixture being too rich, turn
the Mixture Control Valve clockwise about 1/12 turn (30 ).
Normal safe idle speeds are in the region of 2,000 r.p.m..
NOTE:
As this is four-cylinder four-stroke-cycle engine, firing
strokes occur every half revolution (180 ), that is, two
firings take place every one complete revolution.
Therefore, at first you may have an impression that the
engine is idling at higher r.p.m. than actual running r.p.m.
It is recommended to check the engine r.p.m. with a
tachometer.
Changing the make of glowplug or fuel may sometimes
require re-adjustment of carburetor throttle.
Realignment of mixture control valve
In the course of making carburetor adjustments, it is just
possible that the Mixture Control Valve setting may be
upset.Its basic setting can be re-established as follows:
Turn the Mixture Control Valve counter-clockwise until it stops,
then screw it out 3 turns. This is the basic position.
NOTE:
If an on-board glowplug re-heat system is installed,
mixture adjustment at idle speed should be carried out
with this in operation.
27
FLIGHT & MAINTENANCE
It is necessary to warm up the engine as with a full-size
aircraft or automobile. Do not attempt to take-off immediately
after the engine has been started. Allow the engine to run at
full throttle for at least 10 seconds before releasing the model.
Checking before flight
Make sure that all four cylinders are firing.
Make sure that engine runs steadily at idle speed.
Make sure that engine is fully warmed up.
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)
is available as an optional extra.
Install an in-line fuel filter between the tank and carburetor
to prevent foreign matter in the tank from entering the
carburetor.
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.
Clean these filters periodically.
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.
Care and Maintenance
Do not close the needle-valve 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 20-30
seconds with the electric starter. Finally, inject some after-run
oil through the glowplug hole and turn the engine over several
times with the electric starter.
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 with
intake pipe, glow plug and all silicone tubing and put them safely
aside. Then, immerse the engine in a container of alcohol. Rotate
the crankshaft while the engine is immersed. If foreign matter is
visible in the alcohol, rinse the engine again in clean alcohol.
Finally, shake off and dry the alcohol ,and inject some after-run oil
in the glowplug hole and rotate the crankshaft several times by
hand. Reinstall the carburetor with intake pipe and glowplug on the
engine and keep it in a dry place after putting in a vinyl bag.
