O.S. engine FS-70S User Manual

Note: Smaller or larger props than those shown in the list can be
used. However, it should be noted that propeller noise will
increase as the r.p.m. increase.
For safety, keep your face and other parts of the body wel!
away from the propeller when starting the engine or adjust-
ing the needle-valve while the engine is running. Remember
that the propeller turns through a much wider arc with the
large sized propellers that this engine is capable of driving.
Refer to the “Safety instructions and Warnings” leafiet
enclosed.
IMPORTANT: Use well balanced propeilers and spinners only. An
unbalanced propeller or spinner causes vibration and
loss of power.
WARNING: There is always a danger, especially with nylon pro-
pellers (and depending on engine speed and weather
conditions), of the propeller fracturing and a blade
flying off and, obviously, this could cause serious
injury. Therefore, never crouch over the engine when
it is running and keep all onlookers well back and
behind the model. If a spinner is used, make sure
that the spinner notches are large enough to clear the
propeller blades and so do not cut into and weaken
the blade roots when the propeller nut is tightened.
There is also a risk, particularly with four-stroke engines, of
the propeller flying off if the propeller nut loosens due to
detonation or knocking" when the engine is run too lean
or under too heavy a load. Obviously this can also be very
hazardous.
To combat this danger, we have developed the special
Safety Propeller Locknut Assembly supplied with the
FS-70S. This prevents the propeller from flying off, even
if the propeller itself should slip or loosen.
1. Ream the propeller centre hole to 8mm dia. Make sure
that the propeller is properly balanced.
2. Fit the propeller sleeve-nut and washer to the propeller,
screw onto the shaft and tighten firmly with 14mm
wrench supplied.
3. Finally, insert the Safety Propeller Locknut. Tighten
Locknut firmly (but not with excessive force) using
12mm wrench. (see Fig. 2)
Propeller washer
IMPORTANT:
Regardless of the type of propeller
fixing used, make a habit of al-
ways checking the tightness of the
propeller before starting the
engine. Remember that, especially
with wooden propellers, there is a
tendency for the material to
shrink, or for it to be reduced by
the serrated face of the drive hub.
STARTING
It is preferable to use a heavy-duty electric starter, although
hand-starting is also possible, as will be explained in a
moment.
1. Firstly, fit a spinner so
that an electric starter can
be used. The O.S. special
locknut set for spinner,
that is available as an
optional part, enables you
to fit a spinner securely
and easily.
2. Open the throttle so that
the throttle-arm is at one- Starting position
quarter
of
its
full
throw.
Fig.
3
(see Fig. 3).
(a) lf a silencer pressurized fuel system is employed, set
the needle-valve 2 to 2% turns open from the fully
closed position.
(b) If a silencer pressurized fuel system is not employed,
set the needle-valve 3 to 4 turns open from the fully
closed position.
3. Energize the glowplug and apply the electric starter after
making sure that the battery leads are properly connected
for counter-clockwise rotation. If the power of your
starter is insufficient to immediately rotate the engine
freely, turn the propeller clockwise (‘backwards’) until
compression is felt, then, with the propeller in this posi-
tion, try the starter again. This will enable the kinetic
Drive washer
Propeller nut
Locknut
Fig. 2
energy of the rotating propeller to assist in carrying the
engine through its compression stroke. Also, make sure
that your starter battery is in good condition and fully
charged.
CAUTION: Never apply an electric starter with the choke closed.
Such an action will cause an excess quantity of fuel to
be drawn into the cylinder and result in hydraulic
tock that may damage the engine.
4. When the engine starts, keep it running, initially, with
the original needle-valve setting while steadily moving the
throttle to the fully open position. If the engine slows
down because the mixture is excessively rich, close the
needle-valve slowly until the engine runs evenly. Then
disconnect the battery from the glowplug and close the
needle-valve slowly so that revolutions increase. Adjust
the needle-valve gradually. Abrupt adjustment of the
needle-valve may cause the engine to stop.
The above starting procedure is standard for the FS-/0S.
However, the engine may be safely hand started — except
when using a lightweight wooden propeller. For safety,
be sure to use a ‘‘chicken-stick’’. The procedure is as
follows.
1. The propeller should be fixed in such a way that it is
positioned horizontally as compression is first felt when
turning the propeller counter-clockwise.
2. Open the throttle so that the throttle-arm is at one-
quarter of its full throw. (See Fig. 3)
(a)lf a silencer pressurized fuel system is employed,
set the needle-valve 2 to 2% turns open from the
fully closed position.
(b} If a silencer pressurized fuel system is not employed,
set the needle-valve 3 to 4 turns open from the fully
closed position.
3. Prime the engine by closing the choke valve and turning
the propeller through 4 to 5 revolutions, depending on
the length of pipe from tank to carburettor.
4. Turn the propeller counter-clockwise several times so
that fuel is drawn well into the cylinder.
5. Gradually turn the propeller counter-clockwise until
compression is felt. Leave the prop at this position.
6.
Recheck
the
throttle
setting
(approx.
quarter
open).
7. Connect the glowplug battery and, using the chicken-
stick, briskly swing the propeller clockwise from the
position determined above and from the centre of the
right blade. The engine wil! then bounce smartly in the
counter-clockwise direction to the point where ignition
and expansion of the charge takes place. If the engine
stops, make sure that fue! is reaching the carburettor
from the fuel tank, then repeat procedures 3) to 7).
Correct priming is the secret of easy hand-starting.
8. When the engine starts, keep it running, initially, with
the original needle-valve setting. If it slows down because
the mixture is excessively rich, close the needle-valve
slowly until the engine runs evenly. Then disconnect the
battery from the glowplug and close the needle-valve
slowly so that revolutions increase. Adjust the needle-
valve gradually. Abrupt adjustment of the needle-valve
may cause the engine to stop.
9. To re-start the engine when it is hot, after a run, first try
just flipping the propeller, with the throttle in the idling
position, after re-energising the glowplug. If the engine
does not re-start, re-prime it by closing the choke valve
while rotating the propeller once or twice until the
cylinder becomes cool enough for restarting.
CAUTION: Do not connect the glowplug to the battery while
priming.
Note: Excess fuel in the carburettor may drip into the engine com-
partment when the choke valve is reopened. Therefore, it is
advisable to drill a drain hole in the bottom of the engine bay ,
or cowling and to apply fuelproof paint to the surrounding
surfaces to prevent fuel from penetrating the airframe struc-
ture.
RUNNING-IN (“Breaking-in’’)
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 is because the
working parts of a new engine take a little time to settle
down after being subjected to high temperatures and stress.

O.S. engine FS-70S Specifications

General

Brand	O.S. engine
Model	FS-70S
Category	Engine
Language	English