O.S. engine FS-70S User manual

INSTRUCTIONS FOR
0.S.
FS-'70S
FOUR
STROKE
CYCLE
ENGINE
IMPORTANT: Before attempting to operate your FS-705,
please read through these instructions so as to familiarize
yourself with the controls and other features of the engine.
Also, pay careful attention to the recommendations con-
tained in the “Safety Instructions and Warnings” leaflet
enclosed.
INSTALLATION
Use sturdy engine mounting beams: i.e. at least as strong as
would be used for a two-stroke engine of 15cc, or greater,
displacement. Make sure that these beams are firmly
integrated with the airframe, reinforcing the internal sur-
rounding structure as necessary to absorb vibration. Engine
installation should be made in such a way that basic main-
tenance, including the checking and adjustment of valve
clearances, can be conveniently carried out. As an aid to
aligning the engine on its mounting beams, a simple mount-
ing hole template is supplied with the engine.
As an alternative to horizontal beam mounting, a special
O.S. radial motor mount is available, as an optional extra
part, for use where firewall mounting is required.
SILENCER ASSEMBLY
Installation procedure is as follows.
1. Screw the exhaust header pipe into the exhaust port
until it “bottoms”, then unscrew it just sufficiently to
achieve the required exhaust outlet angle. Secure the
pipe in this position by tightening the locknut firmly
against the cylinder head with the wrench supplied.
2. Screw the silencer onto the end of the header pipe and
tighten locknut firmly.
Note: It is advisable to apply silicone sealant at the joints to prevent
leakage of exhaust gas and loosening of nuts.
lg 1 aaa An, hie le! alate
CARBURETTOR THROTTLE
The needle-valve and throttle lever locations are inter-
changeable by reversing the carburettor. This can be done
as follows:
Remove the carburettor carefully by unscrewing the two
screws which secure both carburettor and choke valve. (See
Photo
1.)
If
the
carburettor
remains
difficult
to
remove,
slightly
loosen
the
two
screws
which
secure
the
intake
pipe
to the cylinder head.
After reversing the carburettor, re-insert it into the intake
pipe gently, taking care not to damage the O-ring in the
carburettor by using force.
Intake pipe
Ha Nid ring
Carburettor
fixing screws
Set screw
i Mee lever
Hexagon nut
Cap screw
Choke rubber pad
Photo 1
CHOKE VALVE |
The FS-70S is equipped with a spring-loaded choke valve.
The choke valve operating lever can be located right or
left by transposing the hexagon nut and cap screw.
After
mounting
the
engine
in
the
model,
secure
the
L-shaped
choke
rod
by
tightening
the
set-screw.
If
the
rod
supplied
is
too
long,
reduce
it
to
the
required
length.
If
the
rod
length
is
more
than
40mm
(1%
in.)
its
outer
end
should
be
supported
to
avoid
vibration.
SPECIFICATIONS
11.50 cc (0.702 cu.in.)
25.8 mm (1.016 in.)
22.0 mm (0.866 in.)
2,000 ~ 12,000 r.p.m.
Displacement
Bore |
Stroke
Practical R.P.M.
Output 1.1 BHP/11,000 r.p.m.
Weight 570 g (20.1 oz.)
FUEL TANK
The suggested fuel tank size is 270cc or 9% oz. This will
give approximately 12 minutes running time when some
part-throttle operation is included. Locate the fuel tank so
that the centre line of the tank is 10 to 15mm below the
centre line of the needle-valve.
Note: If the model is left unattended
with the fuel tank filled, fuel
may flow into the carburettor,
causing it to “flood” and
making the engine difficult to
start. Take appropriate action
to prevent this.
FUEL
The FS-70S runs on standard commercially available model
glowplug engine fuel. Fuels containing castor-oil and/or
synthetic lubricants are acceptable, but for the best per-
formance and reliability, a fuel containing 5 — 15% nitro-
methane is recommended.
For consistent performance and long engine life, it Is
advisable to use good quality fuel containing 16 to 20%
lubricant.
(The carburettor is adjusted with a fuel containing 20%
lubricant when the engine leaves the factory.)
(| Centre line
nla
GLOWPLUG
An O.S. Type “F” glowplug is fitted to the engine.
With a four-stroke engine, ignition of the fuel charge takes
place at every fourth stroke of the piston instead of every
second stroke. Because of this, some conventional two-
stroke glowplugs will not suit this engine. For general use,
the special O.S. Type F glowplug is recommended.
PROPELLER
The choice of propeller depends on the design and weight
of the model and on the type of flying envisaged. Deter-
mine the best size and type after practical experiment. As
starting points, suggested propellers are listed below.
For sport & stunt
models
11x8
~
9,12x7
~8
12%
XG
13%x8, 14x7, 11x7 (3-blade)
For
scale
models
12x8
(3-blade),
12%x7
(3-blade)

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.

However, as O.S. engines are made with the aid of the finest
modern precision machinery and from the best and most
suitable materials, only a very short and simple running-in
procedure Is required and can be carried out with the
engine installed in the model.
For running-in, use the same sized propeller as you intend
for flying your model.
Running-in procedure is as follows:
Start the engine and run it for about 5 seconds at around
maximum r.p.m., then open the needle-valve %2 turn to
produce a rich mixture for cooler, slower running, and run
for 20 seconds at this setting. Keep the throttle fully open,
using only the needle-valve to reduce speed. Repeat this
procedure, alternately running the engine fast and slow
with the needle-valve, but gradually extending the short
periods of maximum speed running until two full tanks of
fuel are consumed.
Note: Take care to avoid dusty and sandy locations. Dust and grit
drawn into the engine will seriously damage its working parts.
Following the initial running-in on the ground, the engine
should be given a period of moderately rich running in the
air. For the first flights, set the needle-valve rich, consistent
with adequate take-off power and steady level flight and, if
necessary, readjust the throttle trim on the transmitter so
that the engine does not stop when the throttle is fully
closed.
With each successive flight, close the needle-valve slightly,
until, at the end of 10 flights, the needle-valve is set for
maximum power. The carburettor can now be adjusted for
optimum throttle performance following the instructions
given tn the next section.
Note: Remember that, while the engine is being run-in and the
needle-valve is set on the rich side, the carburettor cannot be
expected to show its best response. Therefore, avoid abrupt
throttle operation at this stage.
ADJUSTING THE CARBURETTOR
The carburettor of your FS-70S has been factory set for the
approximate best result, but the settings may, in some
cases, vary slightly in accordance with fuel and climatic
conditions.
If the desired throttle response is not obtained after the
completion of the running-in period, the carburettor should
be re-adjusted as follows. Please refer to Photos 2 and 3.
Three adjustable controls are provided on this carburettor.
© The Needle-Valve: For adjusting the mixture strength
when the throttle is fully open.
è The Mixture Control Screw: For adjusting the mixture
strength at part-throttle and idling speeds, to obtain
steady idling and smooth acceleration to medium speeds.
@ The Throttle Stop Screw: For establishing the minimum
idling speed. (see Photo 3)
Mixture control screw
Needie valve
Photo 2
1. Set the throttle lever 1/4 open from the fully closed
position (see Fig. 3) and start the engine in the usual
way. It is preferable to have the throttle only slightly
open, to avoid unnecessarily high revolutions when the
engine starts.
2. Now open the throttle fully and gradually close the
needle-valve until the engine is running at its optimum
rp.m. in the air. The needle-valve setting at this time
will be 1/8 to 1/4 open from the maximum r.p.m.
setting.
Note: Make sure that the engine ts fully “run-in” before operating it
continuously at full power. {See RUNNING IN section.)
3. Having set the needle-valve as described above, close the
throttle and run the engine at idling speed for approxi-
mately 5 seconds, then steadily move the throttle to the
fully open position by means of the throttle servo.
(a) If, at this point, the engine hesitates before picking
up speed, with a low-pitched exhaust note and an
excess of exhaust smoke, it is probable that the idling
mixture is too rich. In this case, it will be necessary
to turn the mixture control screw clockwise about 45
degrees.
(b} If, on the other hand, the engine hesitates or even
appears to cease firing for an instant, before in-
creasing speed, it is probable that the idling mixture ts
too lean. In this case, it will be necessary to turn the
mixture control screw counter-clockwise about 90
degrees then turn it clockwise 45 degrees.
Turn the mixture control screw 30 to 45 degrees at a time
in the early stages. When the response improves, turn the
mixture control screw 10 to 15 degrees at atime. Carry
out adjustments progressively and patiently remembering
the symptoms of rich and lean running, quoted above, until
the engine responds quickly and positively to the throttle.
4. The throttle stop screw is for fixing the minimum idling
speed. If, after carrying out mixture adjustments, the
idling speed is found to be too high, the throttle stop
screw should be turned counter-clockwise until the
desired idling speed is obtained.
Note: Once the correct carburettor settings have been established, it
should be unnecessary to alter them. Such slight needle-valve
readjustments as may be required to compensate for varia-
tions in atmospheric conditions, will not normally affect the
other two controls. Slight readjustments may be necessary
for optimum performance if different types of fuel, glow-
plugs or propellers are used. In this case, begin by flying the
model with the needle-valve approximately 1/8 to 1/4 turn
open from the peak r.p.m. as a safety measure, then readjust
as necessary. |
REALIGNMENT OF MIXTURE CONTROL VALVE
In the course of making carburettor adjustments, it is just
possible that the Mixture Control Valve may be tnadver-
tently screwed in or out too far and thereby moved beyond
its effective adjustment range. Please refer to Fig. 4.
Its basic setting can be reestablished as follows:
First screw in the Mixture Control Valve, while looking into
the rotor hole. (See small sketch.) Then, gradually unscrew
the Mixture Control Valve
until ‘A’ is precisely tangential
to the rotor hole (i.e. so that
‘A’ and ‘B’ are superimposed).
Finaily, unscrew the Mixture
Control Valve a further 180°,
as in the main sketch. This is
the basic (factory) setting for
the Mixture Control Valve.
Mixture control
valve
Throttle
rotor hole
CARBURETTOR CLEANLINESS
The correct functioning of
the carburettor depends on
its small fuel orifices remain-
ing clear. The minute particles
of foreign matter that are pre-
sent in any fuel can easily
partially obstruct these
orifices and upset mixture
strength so that engine per-
formance 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 carburettor and, furthermore,
that this filter is frequently cleaned to remove dirt and lint
that accumulates on the filter screen. Finally, ocasionally
Throttle
stop screw
Dirt and fibrous
matter mostly
accumulate here. x
Photo 3

remove the needle-valve holder from the carburettor, using
the wrench supplied, and extract any remaining foreign
matter that may have lodged in the location shown in
Photo 3.
VALVE CLEARANCE ADJUSTMENT
Valve clearances are correctly set before any O.S. four-
stroke engine leaves the factory and, in normal use, will
seldom require adjustment. However, if, after a considera-
ble amount of running time has accumulated, a loss of
power is detected, or if the engine has to be disassembled or
repaired as a result of a crash, valve clearances should be
checked and readjusted as necessary. For checking and
adjusting the valve clearances, a valve adjusting kit, contain-
ing two feeler gauges and two wrenches, is available as an
optional accessory.
Note: Valve clearances on this engine must be checked and re-set
only WHEN THE ENGINE IS COLD.
1. Remove the rocker cover by unscrewing two Allen
screws from the rocker box on top of the cylinder head.
2. Turn propeller until compression is felt, then turn it one
quarter turn and stop. Both valves should now be closed.
3. The required valve clearance is between 0.04 mm and
0.10 mm (.0015 to .004 in.) measured. between the valve
stem and rocker-arm. Use the 0.04 mm (thinner one)
and 0.10 mm (thicker one) feeler gauges to check
clearance. The 0.04 mm feeler should pass through the
gap: the 0.10 mm gauge should not.
4. If the gap is found to be less than 0.04 mm or more than
0.10 mm, carefully slacken the locknut on the rocker-
arm with the 5 mm wrench supplied, turn adjusting
screw with 1.5 mm Allen key to open or close gap, then
retighten locknut.
Finally, re-check gap and readjust if necessary.
IMPORTANT: Incorrect valve clearances may cause. difficult
starting (due to valve not closing property) or loss
of power (due to valve not opening sufficiently).
NEEDLE VALVE EXTENSION
The needle-valve supplied with this engine is designed to in-
corporate an extension so that, when the engine is enclosed
within the fuselage, the needle-valve may be adjusted from
the outside. An L-shaped rod, of 1.6 — 1.8 mm dia. and
appropriate length, should be inserted into the needle’s
centre hole and secured by tightening the set-screw in the
needle-valve knob with the small Allen key provided.
CARE AND MAINTENANCE
To ensure that you obtain long life and peak performance
from your engine, observe the following.
1. Avoid running the engine under dusty conditions. If
necessary, lay a sheet of plywood or hardboard tn front
and under the nose of the model when starting the
engine.
2. Foreign matter in the fuel can cause the carburettor jet
to be partially clogged. Therefore:
e rinse out the fuel tank with methanol or fuel before
installing it
e fit a fuel filter in the fuel delivery tube between tank
and carburettor
ə fit a fuel filter to the outlet of your squeeze bottle, or
to the pump inlet if you use a manual! or electric pump
e do not leave your fuel container open needlessly
e check filters periodically and clean them when necessary.
3. Do not leave raw fuel in the engine at the conclusion of
a flying session: it may cause corrosion. The best practice
is to disconnect the delivery tube from the carburettor
while the engine is running.
Remaining fuel in the tank should also be drained off.
IMPORTANT: After the engine has run dry, liberally inject
corrosion-inhibiting oil or light machine oil into
the crankcase, via the breather hole, until excess oil
runs from behind the drive washer when the engine
is pointed downwards. Rotate the crankshaft to
distribute the oil to the bearings, etc. Failure to
carry out this procedure may cause internal rusting,
resulting in engine malfunction and voiding the
warranty.
4. 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.
5. If the engine is not to be used for a while (more than
two months) remove the glowplug and rinse out the
interior with kerosene (not gasoline), by rotating the
crankshaft. Shake out residue, then inject corrosion-
inhibiting ol or light machine-oi through the exhaust
pipe and breather hole, again rotating the shaft to distri-
bute the protective oil to all working parts.
6. Avoid unnecessary dismantling of your engine.
PARTS LIST
Code No. | Description || Codeno. | Description
44001000 | Crankcass [| 25960000 | intake Valve Assembly
44002000 | Crankshatt | 45361000 | Rocker Arm Assembly
44003200 Piston | 45962000 Camshaft
45103400 Ee a ae A 45564000 Cam Follower
44004000 | Cylinder Head (w/Valve Ass'y) || 44066000 Push Rod
44004100 | Cylinder Heaa || 44066100 Push Rod Cover Assembly
45904200 | Rocker Cover || 24069400 | _ Intake Pipe Assembly
45605000 | Connecting Rod || 24081000 | Carburettor Complete
44006000 | _Piston Pin == 45484000 | Choke Valve Assembly
44008000 | Drive Washer (w/Key) | 71615009 | Glow Plug Type “F”
29008219 | Woodruff Key [| "71905000 | Radial Motor Mount
46120000 | Thrust Washer || "72200060 | Valve Adjusting Kit
45910100 | Safety Propeller Locknut Assembly || *72108100 | Flexible Exhaust Pipe 1111A (120mm)
45913000 | Screw Set || *72108110 | Flexible Exhaust Pipe 1111B (240mm)
44014000 | GasketSet || *72108120 | Flexible Exhaust Pipe 1111C (170mm)
26731002 | Crankshaft Bearing (Front) || *72108130 | Flexible Exhaust Pipe 1111D (330mm)
45630000 | Crankshaft Bearing (Rear) | "45910200 | Locknut Set for Spinner
45231100 | Camshaft Bearing || *45910300 | 5716-M5 Locknut Set
The specifications are subject to alteration for improvement without notice.
GS. Ej NGINE: § MF6.CO.,LTO.
6-15 3-chome Imagawa Higashisumiyoshi-ku
Osaka 546, Japan. TEL. [phone]
FAX. [phone]
*Optional parts
© Copyright 1988 by O.S. Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan.
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