O.S. Engines FT-300 Gemini - Manual (Page 12)

21
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 idling mixture is
too rich. 1.
Fig.25
Mixture Control Screw
Screwdriver
Turn
45-60
In this case, it will be necessary
to turn the Mixture Control Screw
in the reverse direction from the +
mark (i.e. clockwise) to weaken the mixture. About 1/8-1/6
turn (45-60 ) should be sufficient (Fig. 25).
Alternatively, if the engine stops
or is slow to pick up speed,
without smoking or a strong
exhaust note, it is probable that
the idling mixture is too lean. 2.
Fig.26
In this case, it will be necessary
to turn the Mixture Control Screw
in the direction of the + mark (i.e.
counter-clockwise) approximately 1/8-1/4 turn (45-90 )
(Fig. 26).
Thirdly, if revolutions 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 revolutions compared with
previous full-throttle running. The cutting out of the cylinder
may be caused by the idling speed being set too low or the
idling mixture being too rich. 3.
In the case of the idling speed being too low, re-set the
idling position a little higher by means of the throttle trim on
the transmitter. In the case of the idling mixture being too
rich, turn the Mixture Control Screw in the reverse direction
NOTE:
As this is two-cylinder four-stroke-cycle engine, firing
strokes occur every half revolution (360 ), 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 screw
In the course of making carburetor adjustments, it is just
possible that the Mixture Control Screw setting may be
upset.Its basic setting can be re-established as follows:
of the + mark about 1/8-1/6 turn (45-60 ). Normal safe
idling speeds are in the region of 2,000 r.p.m..
Fig.27 Fig.28
With the basic position of
the screw, this pin is located
at the centre.
(The pin is seen if the
throttle lever is removed.)
mark
Throttle lever
Carefully turn the screw in the
direction of the + mark with
the screw-driver supplied until
it stops, then turn back again
exactly two revolutions.
NOTE:
If an on-board glowplug re-heat system is fitted, mixture
adjustment at idling speed should be carried out with this
in operation.
Turn
45-90
22
FLIGHT
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 two cylinders are firing.
Make sure that engine runs steadily at idling speed.
Make sure that engine is fully warmed up.
CARE AND MAINTENANCE
To ensure that you obtain long life and peak performance from
your engine, observe the following
Avoid running the engine under dusty conditions. If
necessary, lay a sheet of plywood or hardboard in front and
under the nose of the model when starting the engine. 1.
Foreign matter in the fuel can cause the carburetor jet to be
partially clogged. 2.
Therefore:
rinse out the fuel tank with methanol or fuel before
installing it
fit a fuel filter in the uel delivery tube between tank and
carburetor
fit a fuel filter to pump inlet of the manual or electric fuel
pump
do not leave your fuel container open needlessly
check filters periodically and clean them when necessary
Do not close the needle-valve to too "lean" a setting. This
will cause the engine to overheat and slow down and also
will generate much nitromethane oxide due to extremely
high temperature which will cause internal rusting of the
engine. Always adjust the needle-valve very slightly to the
"rich" side of the peak r.p.m. setting. 3.
Clean the exterior of the engine with a clean cotton cloth. If
this is not done, oil and dirt will burn onto the outside of the
engine each time it is run and the engine will soon become
blackened 4.
If the engine is not in use for a while (more than two months)
remove the glowplugs and rinse out the interior with
kerosene (not gasoline), by rotating the crankshaft. Shake
out residue, then inject corrosion-inhibiting oil (preferably) or
light machine-oil through glowplug cabities and breather
hole, again rotating the shaft to distribute the protective oil to
all working parts. 5.