O.S. Engines FT-300 User Manual

It is of vital importance, before attempting to
operate your engine, to read the general

'SAFETY INSTRUCTIONS AND WARNINGS'

section on pages 2-4 of this booklet and to
strictly adhere to the advice contained therein.

Also, please study the entire contents of this
instruction manual, so as to familiarize
yourself with the controls and other features
of the engine.

Keep these instructions in a safe place so that
you may readily refer to them whenever
necessary.

It is suggested that any instructions supplied
with the aircraft, radio control equipment, etc.,
are accessible for checking at the same time.

Horizontally-opposed twin-cylinder
overhead-valve four-stroke-cycle

CONTENTS

SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE

INTRODUCTION, TOOLS AND ACCESSORIES

ENGINE PARTS NAME



INSTALLATION,

PROPELLER, FUEL TANK

GLOWPLUGS,

GLOWPLUG HEATING

FUEL AND LUBRICATION, STARTING

RUNNING-IN ("Breaking-in")

THROTTLE VALVE ADJUSTMENT

2-4

5

6-7

8-10

10-11

12

13-14

15-18

18-19

19-21

FLIGHT

CARE AND MAINTENANCE

VALVE CLEARANCE ADJUSTMENT

ENGINE EXPLODED VIEW

ENGINE PARTS LIST

CARBURETOR EXPLODED VIEW &
PARTS LIST

O.S. GENUINE PARTS & ACCESSORIES

ENGINE THREE VIEW DRAWINGS

22

22

23-25

26

27

28

29

30

1

SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR
O.S. ENGINE

Remember that your engine is not a " toy ", but a highly
efficient internal-combustion machine whose power is
capable of harming you, or others, if it is misused or
abused. As owner, you, alone, are responsible for the safe
operation of your engine, so act with discretion and care at
all times.
If at some future date, your O.S. engine is acquired by
another person, we would respectfully request that these
instructions are also passed on to its new owner.

The advice which follows is grouped under two
headings according to the degree of damage or danger
which might arise through misuse or neglect.

WARNINGS

These cover events which might involve serious (in
extreme circumstances, even fatal ) injury.

NOTES

These cover the many other possibilities, generally less
obvious sources of danger, but which, under certain
circumstances, may also cause damage or injury.

WARNINGS

Never touch, or allow any object to come into
contact with, the rotating propeller and do not
crouch over the engine when it is running.

A weakened or loose propeller may disintegrate or be thrown
off and, since propeller tip speeds with powerful engines may
exceed 600 feet(180 metres) per second, it will be understood
that such a failure could result in serious injury, (see 'NOTES'
section relating to propeller safety).

Model engine fuel is poisonous. Do not allow it to
come into contact with the eyes or m o u th . A l w ays
store it in a clearly marked container and out of
the reach of children.

Model engine fuel is also highly flammable. Keep it
away from an open flame, excessive heat, sources
of sparks, or anything else which might ignite it.
Do not smoke or allow anyone else to smoke, near
to it.

Never operate your engine in an enclosed space. Model
engines, like automobile engines, exhaust deadly carbon­monoxide. Run your engine only in an open area.

Model engines generate considerable heat. Do
not touch any part of your engine until it has
cooled. Contact with the muffler(silencer),
cylinder head or exhaust header pipe, in
particular, may result in a serious burn.

2

NOTES

This engine was designed for model aircraft. Do not attempt to use it for any other purpose.

Mount the engine in your model securely, following the manufacturers' recommendations, using appropriate
screws and locknuts.

Be sure to use the silencer (muffler) supplied with the engine. Frequent exposure to an open exhaust may
eventually impair your hearing.
Such noise is also likely to cause annoyance to others over a wide area.

If you remove the glowplug from the engine and check its condition by connecting the battery leads to it, do not hold
the plug with bare fingers.Use an appropriate tool or a folded piece of cloth.

Install a top-quality propeller of the diameter and pitch specified for the engine and aircraft. Locate the propeller on
the shaft so that the curved face of the blades faces forward-i.e. in the direction of flight. Firmly tighten the propeller
nut, using the correct size wrench.

Always check the tightness of the propeller nut and retighten it, if necessary, before restarting the engine,
particularly in the case of four-stroke-cycle engines. If a safety locknut assembly is provided with your engine,
always use it. This will prevent the propeller from flying off in the event of a "backfire", even if it loosens. Also,
check the tightness of all the screws and nuts before restarting the engine.

If you install a spinner, make sure that it is a precision made product and that the slots for the propeller blades
do not cut into the blade roots and weaken them.

Discard any propeller which has become split, cracked, nicked or otherwise rendered unsafe. Never attempt to
repair such a propeller: destroy it. Do not modify a propeller in any way, unless you are h igh ly experienced in tuning
propellers for specialized competition work such as pylon-racing.

3

NOTES

Use an electric starter for this engine. The wearing of safety glasses is also strongly recommended.

Take care that the glow plug clip or battery leads do not come into contact with the propeller.
Also check the linkage to the throttle arm. A disconnected linkage could also foul the propeller.

After starting the engine, carry out any needle-valve readjustments from a safe position behind the rotating
propeller. Stop the engine before attempting to make other adjustments to the carburetor.

Adjust the throttle linkage so that the engine stops when the throttle stick and trim lever on the transmitter are fully
retarded. Alternatively, the engine may be stopped by cutting off the fuel supply. Never try to stop the engine
physically.

Take care that loose clothing (ties, shirt sleeves, scarves, etc.) do not come into contact with the propeller.
Do not carry loose objects (such as pencils, screwdrivers, etc.) in a shirt pocket from where they could fall through
the propeller arc.

Do not start your engine in an area containing loose gravel or sand. The propeller may throw such material in your
face and eyes and cause injury.

For their safety, keep all onlookers (especially small children) well back (at least 20 feet or 6 meters) when preparing
your model for flight. If you have to carry the model to the take-off point with the engine running, be especially
cautious. Keep the propeller pointed away from you and walk well clear of spectators.

Warning! Immediately after a glowplug-ignition engine has been run and is still warm, conditions sometimes exist
whereby it is just possible for the engine to abruptly restart if the propeller is casually flipped over compression
WITHOUT the glowplug battery being reconnected. Remember this if you wish to avoid the risk of a painfully rapped
knuckle!

4

INTRODUCTION

The O.S. FT-300 (Super Gemini-300) is a horizontally­opposed twin-cylinder overhead-valve four-stroke­cycle engine of 48.76cc (2.976cu.in) displacement.
The horizontally-opposed layout, typical of modern
light aircraft engine design, provides very smooth
running qualities and docile, trouble-free handling
characteristics.

Photos and illustrations in this manual show FT-160.
It's appearance a little differs from that of FT-300.

TOOLS AND ACCESSORIES

The following tools and accessories are supplied with your
engine.

No.

Mount fixing screw (M5X25)

1

Lock washers (ø5)

2

Blind nuts (M5)

3

Set of leads for wiring glow plugs

4

Leads for glow plug with clip

4-1

Lead for earth (ground)

4-2

Woodruff key

5

Valve adjusting tool kit

6

Choke valve rod

7

Description

Quantity

6
6
6

2
1
1
1
1

7

3

2

4-2

4

6

5

4-1

1

Photo 1

5

ENGINE PARTS NAME

Photo. 2

Right (No.2) Cylinder

Crankcase

Aluminum tube

Propeller Nut

Lock Nut

Propeller Washer

Drive Hub

Left (No.1) Cylinder

Cylinder Head

Glow Plug

Rocker Cover

Exhaust Pipe

Carburetor

Photo shows FT-160.

Aluminum tube is not supplied with the engine.

Intake Manifold

Breather Nipple

6

Choke V alve

Fuel Inlet

Push Rod Cover

Photo. 3

Intake Pipe (Right)

Intake Pipe (Left)

Rear Housing

Photo shows FT-160.

7

INSTALLATION

It is essential that the firewall is strong and rigid (e.g. at
least 15mm thick) and firmly integrated with the structure of
the aircraft.

In the interests of scale appearance, the engine should be
installed with the carburetor below the crankcase so that
the exhaust pipes point downwards.

Note:

Make sure that the firewall is all flush and front face and
rear face are parallel. Do not dismantle the engine from
the radial mount when installing the radial mount to the
firewall.
Before installing the engine on the radial mount after
dismantling it from the mount, make sure both arms are
flush and parallel.

M5 Blind nut

M5x25 screw

5 Lock washer

Firewall

Needle-valve extension

The needle-valve with this engine is designed to incorporate
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 1.6-1.8mm 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. For
longer extension, it is recommended to use the extension
cable with the engine, together with the knob and support
hook also. For this purpose, Needle Valve Extension Cable
Set (Code No. 72200080) is available as an optional part.

Do not use an excessively long unsupported extension as
this may vibrate and cause the needle-valve setting to vary
or even damage the needle-valve thread. Always provide a
suitable support at the outer end.

Set-screw

Set-screw

Hook

At least 15mm (0.6")
rigid hard wood Fig. 1

Choke valve

The choke valve operating lever can be located rught or left
by reversing the hexagon nut nd cap screw.

Unscrew the cap screw while holding the hexagon nut with
6mm wrench, and re-fit the lever to required location.

If the rod is too long, reduce it to required length.
A needlessly lengthy rod may vibrete. The rod should be as

short as possible or have its outer end supported.

Choke lever

Set-screw

Hex. nut

Cap screw

Choke rubber pad

Fig. 3

Fuel inlet

The fuel inlet nipple on the carburetor can be adjusted to the
most suitable position for connecting to the fuel delivery tube
from the tank. Slacken the needle-valve holder with the 8mm
wrench provided, reset the inlet nipple at the required angle
and re-tighten.

Needle

Cable

Knob

Fig. 2

8

Exhaust pipe adjustment

The direction of the exhaust
pipes may be altered in
accordance with individual
installation requirements. The
angle is easily adjusted by
loosening the nut that secures
the exhaust pipe to the cylinder
head. Use the 12mm wrench
supplied.

12mm wrench

Loosen

Lock nut

Exhaust pipe

Fig. 5

Tighten

Carburetor cleanliness

It is recommended that the 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.

Occasionally remove the needle-valve holder from the
carburetor and rinse out the locaions shown in Fig. 6 and
Fig. 7 with methanol or fuel. Be careful not to lose the
gasket when removing the needle-valve holder from the
carburetor.

Fig. 6

Squeeze bottle

Fig. 7

Slacken with 8mm wrench

Fuel inlet

Needle-valve

Fig. 4

Dirt and fibrous matter
mostly accumulate here.

Dirt and fibrous matter
mostly accumulate here.

Needle-valve holder

9

Carburetor

The needle-valve and throttle lever locations are
interchangeable by reversing the carburetor. This can be
done as follows:
Remove the carburetor carefully by unscrewing the two
screws which secure both carburetor and choke valve.
After reversing the carburetor, re-insert it into the intake
manifold, taking care not to damage the O-ring in the
manifold.

Choke valve

Carburetor retaining screw

Photo. 4

PROPELLER

The choice of propeller depends on the design and weight of
the aircraft and on the type of flying in which you will be
engaged. Determine the best size and type after practical
experimentation. As a starting point, refer to the props listed in
the accompanying table. Slightly larger, or even slightly
smaller, props than those shown in the table may be used, but
remember that propeller noise will increase if blade tip velocity
is raised, due to higher rpm or if a larger-diameter / lower-pitch
prop is used.

Warning:

Make sure that the propeller is well balanced. An
unbalanced propeller and / or spinner can cause serious
vibration which may weaken parts of the airframe or
affect the safety of the radio-control system.
DO NOT forget the WARNINGS and NOTES on propeller
and spinner safety given on pages 2,3 and 4.

Intake manifold

PROPELLER & SPINNER ATTACHMENT

There is a risk, particularly with powerful four-stroke engines,
of the propeller flying off if the prop nut loosens due to
detonation ("knocking") in the combustion chamber when the
engine is operated too lean, or under an excessively heavy
load.

Obviously, this can be very hazardous. To eliminate such
dangers, the O.S. Safety Locknut Assembly was devised.
Install this as follows:

1.

Ream the propeller shaft hole to 13.5mm bore with an
appropriate reamer, checking that the hole is exactly
centered.

2.

Install the prop to the engine shaft, followed by the retaining
washer and prop nut and tighten firmly with a 17mm
wrench. (not supplied).

Type

Sport/Scale

NOTE:
Make a habit of always 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. Retighten the propeller nut
if necessary after loosening the Safety Propeller Locknut.
The licknut should be tightened firmly after retightening
the propeller nut.

Size (DxP

18x10-12, 20x8-10, 22x8

)

10

Propeller washer

Propeller nut

Locknut

Propeller washer

Locknut

Propeller nut

Back-plate of spinner

Drive hub

The Safety Propeller Locknut can
be used provided that the width is
between 21.5mm and 26mm.

Drive hub

Fig. 9

3.

Add the special tapered and slotted locknut and secure
with a 13.5mm wrench while holding the prop nut with the
14mm wrench. (not supplied).

To be equal

To be equal

Ream to 13.5mm dia.

Fig. 8

FUEL TANK

The suggested fuel tank size is 400cc or 14 oz. This will give
approximately 10 minutes running time at full power, or about
13-15 minutes when some part-throttle operation is included.
Fuel consumption also depends, of course, on the size of
propeller used.

The ideal fuel tank location is with the top of the tank 5-10mm
(1/4-3/8") above the needle valve. However, model design will
usually require the tank to be located higher than this and there
should be no trouble with such a tank location provided that
you do not pursue spectacular aerobatic flight.
If the tank is located high, fuel will flow into the carburetor when
the tank is full. Therefore, pinch the fuel line with a clip, when
the engine is not running, to prevent flooding and loss of fuel.

11

GLOWPLUGS

The FT-300 is supplied with an O.S. Type F glowplug,
specially designed for O.S. four-stroke engines.

The role of the glowplug

With a glowplug engine, ignition is initiated by the application
of a 1.5-volt power source. When the battery is disconnected,
the heat retained within the combustion chamber remains
sufficient to keep the plug filament glowing, thereby continuing
to keep the engine running. Ignition timing is 'automatic' :
under reduced load, allowing higher rpm, the plug becomes
hotter and, appropriately, fires the fuel/air charge earlier;
conversely, at reduced rpm, the plug becomes cooler and
ignition is retarded.

Glowplug life

Particularly in the case of very high performance engines,
glowplugs must be regarded as expendable items.

However, plug life can be extended and engine performance
maintained by careful use, i.e.:

Install a plug suitable for the engine.
Use fuel containing a moderate percentage of nitromethane

unless more is essential for racing events.
Do not run the engine too lean and do not leave the battery

connected while adjusting the needle.



When to replace the glowplug

Apart from when actually burned out, a plug may need to be
replaced because it no longer delivers its best performance,
such as when:

Filament surface has roughened and turned white.
Filament coil has become distorted.

Foreign matter has adhered to filament or plug body has
corroded.

Engine tends to cut out when idling.
Starting qualities deteriorate.

12

GLOWPLUG HEATING

Glowplug battery

It is necessary to use a glowplug
battery of fairly large capacity (10Ah
or more) as this is required to heat
two glowolugs simultaneously.
A heavy-duty 1.5-volt dry battery or
(preferably) 1.2-volt Ni-Cd battery
may be used.

A 2-volt lead-acid cell (accumulator) may also be used but
only if porvision is made for reducing the voltage at the plugs
since these are nominally rated at 1.5-volt. See notes below.

The two glowplug leads supplied with the engine should be
brought together (Fig.13) and connected to a conveniently
located common external point on the fuselage. This can
either be a terminal with a separate terminal for the earth
(ground) lead (Fig.10) or a suitable socket or jack with
connections for both glowplug and earth (ground) leads
(Fig.11) . Note that the earth (ground) lead supplied is much
heavier (2.0 mm multi-strand copper core) than the plug
leads as this has to have the capacity to carry the current for
all two plugs. Similar wire should be used if a single lead is
employed to extend the glowplug leads (Fig.13).

Heavy-duty 1.5-volt dry battery

Use at least four heavy-duty cells wired in parallel (Fig.9)
and with short heavy leads (to minimize voltage drop) to the
connection point on the fuselage. The disadvantage of dry
cells is that they cannot be recharged when their power
diminishes and makes the engine difficult to start.

2

Heavy-duty dry batteries

Fig. 9

Ni-Cd (nickel-cadmium) 1.2-volt rechargeable battery

Use a 10-Ah cell, or 8 to 10 1.2-Ah cells (as commonly used
for electric-powered R/C cars) wired in parallel and with
short heavy leads (to minimize voltage drop) to the
connection point on the fuselage.

Lead-acid 2-volt rechargeable cell

A lead-acid cell of 10-Ah (preferably greater) capacity is
required. However, in this case, it is necessary to reduce
the applied voltage at the glowplugs to approximately 1.5
volt. The recommended method is to insert a suitable
resistor in each individual plug lead. It is possible, of course,
to use a rheostat attached to the 2-volt cell, or to use extra
long leads (at least 2 metres) to obtain the required voltage
drop. However, the disadvantage of this method is that if
one glowplug should fail or become disconnected, voltage
to the other three will be increased with the risk of burning
out their elements.

1. Fit terminals to the fuselage.

1.5V

Fig.10

2. Fit a jack to the fuselage.

1.5V

Fig.11

13

Glowplug leads

The plug leads are fitted with special snap-on connectors
that ensure firm contact with O.S. plug. They are a "click" fit
and are not suitable for use with most other makes of
glowplug.

The earth (ground) lead is fitted with a plug terminal which
should be connected to the engine by means of one of the
mounting screws.

Make sure that no part of the wiring touches the cylinder
head or cooling fins.

Keep wiring away from the fuel tank where it might cause a
fire in the event of a short-circuit.

Fig.12
Install Ni-Cd battery in the fuselage, and switch on or off by

means of transmitter. (On-board battery)

Switch should have
sufficient capacity.

1.2 volt Ni-Cd battery with
more than 6 Ah capacity.

If glowplug leads are extended together as a single cable,
use heavier wire, e.g. 2.0 mm multi-strand copper core as
supplied for earth lead.

2.0mm

Glowplug re-heat

Under normal conditions, the FT-300 will idle sufficiently
slowly with the throttle closed to permit a safe landing
approach. However, if conditions (atmospheric, fuel, tank
location etc.) are unfavourable, there may be a tendency for
one cylinder to cease firing if the engine is throttled down to a
very low idling speed. This can be prevented by installing a
small on-board Ni-Cd battery which will automatically re-heat
the glowplugs when the engine is throttled down to idling
speed (Fig.12). A suitable switch should be installed so that it
is actuated by the throttle servo only when the engine is
throttled down. Safe idling speeds of less than 1,800 rpm may
be obtained in this way and without undue drain on the
battery.

2

2

Fasten to the
motor mount.

Earth lead

Fig.13

FUEL AND LUBRICATION

Fuel

The FT-300 should be operated on a methanol based fuel
containing not less than 18% (volumetric) castor oil, or a top
quality synthetic lubricant (or a mixture of both), plus a small
percentage (5-20%) of nitromethane for improved flexibility
and power.

Reminder!

Model engine fuel is poisonous. Do not allow it to
come into contact with the eyes or mouth. Always
store it in a clearly marked container and out of the
reach of children.

Model engine fuel is also highly flammable. Keep it
away from open flame, excessive heat, sources of
sparks, or anything else which might ignite it. Do not
smoke, or allow anyone else to smoke, near to it.

Lubrication

All parts of the FT-300 are automatically lubricated by the oil
content of the fuel mixture.

The crankcase breather hole is located at the side of the
engine and is fitted with a brass nipple. (See photo 3 on page

7.) Fit a length of silicone tubing of approx. 2.5-3mm I.D. to
this nipple to conduct away the small amount of oil that
escapes through the breather.

Make a habit of draining out the excess oil in the crankcase
at the end of each flying session. Leaving contaminated oil in
the crankcase for a long time will cause rust. Also, residual
castoroil will tend to solidify and lock the engine. Inject
corrosion-inhibiting oil into the crankcase to neutralize the
effects of any remaining contaminants.

14

STARTING

Precautions

For safety, please observe the following instructions before
starting the engine.

Starting procedure is as follows:

1.

Start the engine by turning the propeller counter-clockwise
(i.e. normal running direction).

Do not start the engine with the throttle fully opened,
otherwise the model will tend to move forward suddently due
to the strong thrust of the propeller. Hold both wings of the
model when starting the engine.

Do not carry out carburetor adjustments (except needle­valve adjustment) while engine is running.

Use a high-torque electric starter.

Open the needle-valve 3 to 3.5 turns from the fully closed
position (Fig.14).

open 3 to 3.5 turns.

Fig.14

15

Make sure that glowplugs are not connected to the battery.

2.
Do not heat the glowplugs while priming. (Fig.15).

Do not connect the battery to
the glowplugs while priming.

If very strong compression is felt when trying to turn the
propeller counter-clockwise, too much fuel has been drawn
into the engine. In this case, do not use force, but release
the choke valve and turn the propeller clockwise slowly to
eject excess fuel through exhaust pipes.

Fig.18

Fig.15

Open the throttle valve fully, close the choke valve and turn

3.
the propeller counter-clockwise through three revolutions.
(Fig.16 & 17)

Fig.16

Close the choke valve.

Open the throttle fully.

Fig.17

Turn 3 revolutions.

Do not apply the starter with the choke closed.

Warning! Never close the choke valve when applying the
starter. Such an action will cause an excess quantity of fuel
to be drawn into the cylinder and result in hydraulic lock that
may damage the engine. (Fig.18)

Excess fuel in the carburetor may drip into the engine
compartment 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 structure.

Release the choke

4.
control and immediately
turn the propeller
counter-clockwise
several times so that fuel
is drawn well into the
cylinders (Fig.19).

Fig.19

16

Set the throttle valve

5.
approximately 1/4 open from
the fully closed position.
(Fig.20).

Starting with an electric

6.

starter (Fig.21)

Make sure that the direction of rotation of the starter is
correct.

Connect the glowplug battery.
Apply the electric starter.

Connect the battery to the glowplug.

Make sure that the direction
or rotation is correct.

When the engine starts,

7.

open the throttle valve fully
and keep it running initially
(approx. 10 seconds), with
original needle-valve setting.

Fully open

Set at this position

Electric starter

Open the throttle fully.

Fig.20

Fully closed

Fig.21

Fig.22

Make sure that all two cylinders are firing

8.
The engine is running properly if white smoke is emitted

through all four exhaust pipes. A slight spray of fuel will be
discharged through the exhaust pipe or any cylinder that is
not firing.

If a cylinder ceases firing, reduce the throttle setting to
approximately 1/4 open from the fully closed position and
re-connect the glowplug battery. Revolutions will increase
when all cylinders are firing steadily.

Fig.23

A slight spray of fuel may be emitted through the exhaust
pipe if a cylinder is not firing.

Now disconnect the glowplug battery.

9.

17

Adjust the needle-valve

10.
Abrupt adjustment of the needle-valve may cause the

engine to stop, especially when it is new and insufficiently
run-in.

As the speed of the engine does not instantly change with
needle-valve readjustment, small movements, with pauses
between, are necessary to arrive at the optimum setting.

Practical best (optimum) needle-valve setting

Close the needle-valve
gradually and slowly.

Approx. 40

Maximum rpm setting
("Lean")

"Rich" needle-valbe setting
when starting the engine.

RUNNING-IN ("Breaking-in")

Obtain a 20x8 propeller for running-in.

1. Running-in on the ground

Start the engine

↓

1

Set the needle-valve at 500-1,000r.p.m. lower than
maximum r.p.m. setting and run approx, 10 seconds.
(It is suggested to use a tachometer.)

↓

2

Open the needle-valve at approx. 1,000r.p.m. lower
than above setting and run approx. 20 seconds.

Engine stops.

Re-starting the engine when warm

To re-start the engine when warm, simply re-energise the
plugs and reapply the starter with the throttle in the idling
position. If the engine does not start, disconnect the battery
from the glowplugs and re-prime by closing the choke valve
while rotating the propeller twice with the throttle open.
Initially, the high temperature inside the combustion chambers
may turn the liquid fuel into gas and emit it through the
exhaust pipes. Therefore, repeat the priming procedure once
or twice until the cylinders become cool enough for restarting.

2. Running-in in the air

Start the engine

Fly the model.

Set the needle-valve approx 40 open from optimum
position (approx. 40 open from maximum r.p.m.).

Revolutions start to decrease.

Fig.24

Repeat above procedure, while increasing the setting 1 r.p.m.
gradually, for approx. 10 minutes.

NOTE:

Keep the throttle fully open, using only the needle-valve to
change r.p.m. Prolonged running-in on the ground is not
suggested because the purpose is just initial running-in
to increace engine temperature gradually close to that of
maximam r.p.m.

18

THROTTLE VALVE ADJUSTMENT

Needle-valve adjustment

Adjust the needle-valve following the instructions given in
STARTING section.

Mixture control screw

Photo. 5

NOTE: Avoid prolonged heavy load flight.

With each successive flight, close the needle-valve
slightly, until, at the end of 10 flight, the needle-valve is
set for optimum position.

Finish running-in.
The carburetor can now be adjusted for optimum throttle

performance following the instructions given in the next
section.

Needle-valve

Fuel inlet

Throttle stop screw

Mixture control valve adjustment

After running is completed and the needle-valve is set at
optimum position (approx 40 open from maximum r.p.m.
position), check the idling running and adjust only when
necessary.

Choke valve

19

Start the engine.

20

Re-set the idling position at
a little higher r.p.m.

Engine stops.

open the throttle fully .

Adjust the neede-valve.

Close the throttle gradually.

Find the idling position.

Fix the idling position.

Open the throttle fully.

Does the engine
regain full power?

Yes.

Continue running at high speed
for 5 seconds.

Close the throttle.

Run at idling speed for 5 seconds.

Disconnect the glowplugs from the battery.

Approx 40˚ open from maximum
r.p.m. setting.

Make sure that all 2 cylinders are firing.

The position where the lowest
possible r.p.m. ,with steady
running, is obtained.
Set the throttle opening by
means of the throttle trim on
the transmitter so that the lowest
practical speed, without risk of
the engine stopping,is obtained.

Make sure glowplug heat is switched.

The engine hesitates before picking
up to full speed, or appears to run at
medium speed with reduced power.

Check mixture adjustment at idling
speed. Make sure that all cylinders
are firing.

Adjustment should be carried
out after stopping the engine.

Do not move needle-valve
while adjusting other controls.

Engine stops.

Attention: Do not leave the battery connected while adjusting the carburetor.

Does the engine stop?

No.

Apply full throttle.

Does the engine
regain full power
immediately?

Yes.

OK

Repeat the procedure while opening and closing the

throttle until the best result is obtained.

Adjusting the mixture control valve

If the engine hesitates, puffing out

1.
a good deal of smoke, before
picking up to full speed, it is
probable that the idling mixture is
too rich.

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

2.
or is slow to pick up speed,

without smoking or a strong
exhaust note, it is probable that
the idling mixture is too lean.

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

3.
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.

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

Mixture Control Screw

Turn
45-60

Screwdriver

Fig.25

Fig.26

Turn
45-90

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..

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:

With the basic position of
the screw, this pin is located
at the centre.

(The pin is seen if the
throttle lever is removed.)

Fig.27

+

mark

NOTE:
If an on-board glowplug re-heat system is fitted, mixture
adjustment at idling speed should be carried out with this
in operation.

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.

Throttle lever

21

Fig.28

FLIGHT

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.
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.

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

1.
necessary, lay a sheet of plywood or hardboard in front and
under the nose of the model when starting the engine.

Foreign matter in the fuel can cause the carburetor jet to be

2.
partially clogged.

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

3.

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.

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

If the engine is not in use for a while (more than two months)

5.
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.

22

VALVE CLEARANCE ADJUSTMENT

ALL O.S. four-stroke engines have their valve (tappet)
clearances correctly set before they leave the factory.
However, if, after many hours of running time have been
logged, a loss of power is detected, or if the engine has to
be disassembled or repaired as a result of an accident,
valve clearances should be checked and readjusted, as
necessary, with the aid of the O.S. Valve Adjusting Tool Kit.

The kit comes in a plastic case and includes:

Hex. key 1.5mm

Wrench 5mm

Feeler gauge 0.04mm
Feeler gauge 0.1mm

2.

Remove all the glowplugs except the one fitted to the
cylinder that you want to check.

Note:
Each glowplug should be re-fitted to the original cylinder.
You may start to check and adjust with any cylinder.

3.

Turn the propeller counter-clockwise until compression is
first felt, then turn it futher quarter turn. At this point, both
valves should be closed. (If the prop driver ('drive hub') of
your engine is engraved with a letter 'T', this mark should
now be at the top.)

4.

The standard valve clearance, on both inlet and exhaust
valves, is between 0.04mm and 0.1mm(0.0015-0.004 inch),
measured between valve stem and rocker arm. Use the

0.04mm and 0.1mm feeler gauges to check clearances.
(See Fig.29.)

Note:
Valve clearances of all O.S. four-stroke-cycle engines
must be checked and reset ONLY WHEN THE ENGINE IS
COLD. Procedure is as follows:

1.

Remove the rocker cover from each cylinder head by
unscrewing two socket-head cap-screws from the rocker
box on top of the cylinder head with Allen key supplied.

Note:
If the gap is found to be less than 0.04mm, it is not
necessary to readjust the clearance if the engine has
good compression and starts easily. Equally, if the gap
exceeds 0.1mm but is not more than 0.14mm (i.e. the
thickness of both feeler gauges inserted together), it is
not necessary to readjust the clearance if the engine
runs satisfactorily.

0.04mm Feeler Gauge
Rocker Arm

Valve

23

Turn adjusting-screw approx. 1/2 turn counter-clockwise to

2.
open gap, using appropriate tool -i.e. Allen hex key. (Fig.3.)

Adjusting Screw

Turn approx.1/2 turn.

Allen Key

Fig.29

If a clearance is found to be outside either of these limits, it
should be reset as follows.

1.

Carefully loosen the locknut on rocker-arm 1/4-1/2 turn with
5mm wrench. (Fig.30.)

Locknut

Slacken approx.1/4 to 1/2 turn.

Wrench

Fig.30

3.

Insert 0.04mm feeler gauge between valve stem and rocker­arm and gently turn adjusting screw clockwise until it stops.
(Fig.32.)

Turn with fingers until it stops.

0.04mm Feeler Gauge

24

Fig.31

Fig.32

Re-tighten locknut while holding adjusting screw stationary.

4.
(Fig.33.)

Hold at the screw head.

Tighten Locknut.

5.

Remove 0.04mm feeler, rotate prop through two
revolutions and recheck gap.

If clearance is correct, loosen the locknut on the other

6.

rocker-arm and repeat steps 1 to 5 above. Finally, replace
rocker box cover.

Remember:
Excessive valve clearance will cause loss of power, due
to valve (s) not opening sufficiently. On the other hand, a
total loss of clearance may cause difficult starting due to
valves not closing properly, resulting in loss of
compression.

Fig.33

25

EXPLODED VIEW

29

31

13-2

13

13-1

10-2
10-1
10-3

11

10

40

36

30

39

38

41

37

34

30-1

33

32

17

16-2

16-1

16

C.M3x8

10-2

C.M4x12

25

16-3

14-2

14-1

35

28

27

26

1

24

23

15

22

21

14

8

4-1

19

20

18

C.M3.5x15

M3

C.M3.5x12

C.M3x20

9

7-2

7-1

1

C.M5x12

4

5

6

7

4-2

3-2

4-3

3

3-1

42

4-4

C.M4x18

C.M4x25

1

2

C.M2.6x12

PARTS LIST

No.

1
2

3
3-1
3-2

4
4-1
4-2
4-3
4-4

5

6

7
7-1
7-2

8

9

10
10-1
10-2
10-3

11

12

13
13-1
13-2

14
14-1
14-2

15

16
16-1
16-2

Code No.

46213000
46204200
45561010
45561110
45061202
46260010
46260110
45560200
45060309
46160400
45661500
26381501
46269000
46269100
46269200
46204110
46204020
46268000
46268010
46268020
46215000
46281000
46184000
46268100
46268110
46269200
46268200
46268210
46269200
46266000
46266100
46266110
45566300

Screw Set
Rocker Cover
Rocker Arm Assembly (1pair)
Rocker Arm (1pc.)
Tappet Adjusting Screw
Valve Assembly (1pair)
Valve (1pc.)
Valve Spring (1pc.)
Spring Seat (1pc.)
Valve Spring Retainer (2pcs.)
Rocker Shaft
Rocker Shaft Fixing Screw
Exhaust Pipe Assembly
Exhaust Pipe
Exhaust Pipe Lock Nut
Cylinder Head
Cylinder Head (W/Valve Assembly)
Intake Manifold Assembly
Intake Manifold
Intake Pipe "O" Ring (2pcs.)
Carburetor Rubber Gasket
Carburetor Complete
Choke Valve Assembly
Intake Pipe Assembly (right)
Intake Pipe (right)
Intake Pipe Lock Nut
Intake Pipe Assembly (left)
Intake Pipe (left)
Intake Pipe Lock Nut
Push Rod (2pcs.)
Push Rod Cover Assembly (2pcs.)
Push Rod Cover (1pc.)
Push Rod Cover "O" Ring (L) (2pcs.)

12

N.+M3x22

Description

26

No.

16-3

17
18
19
20
21
22
23
24
25
26
27
28
29
30

30-1

31
32
33
34
35
36
37
38
39
40
41
42

Type of screw

C...Cap Screw M...Oval Fillister-Head Screw
F...Flat Head Screw N...Round Head Screw S...Set Screw

Code No.

24881824
45564000
46203400
46203210
29406000
29017004
46205000
46214010
46203110
46203310
46031005
46262000
22631019
46210100
46208000
29208200
46231000
46201010
26530008
46202000
29030001
46201700
46202200
46202100
46202300
46201810
45471000
71911000
71615009
72200090
72200060

Push Rod Cover "O" Ring (S) (2pcs.)
Cam Follower (2pcs.)
Piston Ring
Piston
Piston Pin
Piston Pin Retainer
Connecting Rod Assembly
Head Gasket Set (2pcs.)
Cylinder Liner
Cylinder Jacket
Camshaft Bearing (front)
Camshaft
Camshaft Bearing (rear)
Propeller Locknut Set
Drive Hub
Woodruff Key
Crankshaft Bearing (front)
Crankcase
Crankshaft Bearing (intermediate)
Crankshaft
Crankshaft Bearing (rear)
Bearing Holder
Drive Gear Key
Drive Gear
Drive Gear Fixing Screw
Rear Housing
Breather Nipple (No.4)
Radial Motor Mount Set
Glow Plug Type F
Booster Cable Set
Valve Adjusting Kit

The specifications are subject to alteration for improvement without notice.

Description

27

CARBURETOR EXPLODED VIEW & PARTS LIST

S.M3x3

1

2-1

S.M3x3

3-1

3

S.M3x3

4-1

5

4

7-1

6

8

7

11

10

9-6

9-5

12

9-4

N.+M3x22

2

Note: The choke valve assembly is not included in the carburettor complete.

Type of screw
C...Cap Screw M...Oval Fillister-Head Screw

F...Flat Head Screw N...Round Head Screw S...Set Screw

9-7

No.

Code No.

26381501

1

24981405

2

26381501

2-1

46281320

3

22781800

3-1

46281330

4

26381501

4-1

46281200

5

46281340

6

46281310

7

22781800

S.M3x3

9-2

9

9-3

9-1

7-1

8

9
9-1
9-2
9-3
9-4
9-5
9-6
9-7

10
11
12

46281100
46281900
29081952
24981837
26381501
46181940
46181941
46181950
26711305
45681600
45581820
45581700

Set-screw
Throttle Lever Assembly
Set-screw
Mixture Control Screw Assembly
"O" Ring (2pcs.)
Mixture Control Screw Holder Assembly
Set-screw
Carburetor Rotor
Mixture Control Valve Pin
Mixture Control Valve Assembly
"O" Ring (2pcs.)
Carburetor Body
Needle Valve Assembly
Needle Assembly
"O" Ring (2pcs.)
Set-screw
Needle Valve Holder Assembly
Needle Valve Holder
Fuel Inlet
Ratchet Spring
Throttle Stop Screw
Rotor Guide Screw
Carburetor Retaining Screw

The specifications are subject to alteration for improvement without notice.

Description

28

O.S. GENUINE PARTS & ACCESSORIES

O.S.GLOW PLUG TYPE F

(71615009)

BOOSTER TERMINAL KIT

(72200130)

RADIAL MOTOR MOUNT

(71911000)

3/8"-M5 (L) PROPELLER
LOCKNUT SET FOR 4C SPINNER

(46210300)

BOOSTER CABLE SET

(72200090)

VALVE ADJUSTING
TOOL KIT

(72200060)

BLIND NUT (10pcs.)

M5

(79870050)

NON-BUBBLE WEIGHT

(71531000)

LOCK WASHER (10sets)

M5

(55500004)

FLEXIBLE EXHAUST PIPE

Type

Code.No.

72108200
72108210
72108230
72108240

1114A
1114B
1114C
1114D

Length

120
240
170
330

(mm)

SUPER FILTER (L

(72403050)

)

CAP SCREW SET (10pcs.)

LONG SOCKET WRENCH
WITH PLUG GRIP

M2.6x12
M3.5x12
M3.5x15

(79871040)

(79871080)
(79871090)

The specifications are subject to alteration for improvement without notice.

(71521000)

29

THREE VIEW DRAWING

Specifications

Displacement
Bore
Stroke
PracticalR.P.M.
Output
Weight

24,38cc x 2/1.488cu.in. x 2
33,6mm/1.323in.
27,5mm/1.083in.
1,800-9,000r.p.m.

1,828g/64.5oz.

Dimensions (mm)

45

10

45

102

62

80

90

102

45

45

92

148

56

6 -5.5

90

240

30

C

Copyright 2005 by O.S.Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan.

6-15 3-Chome Imagawa Higashisumiyoshi-ku
Osaka 546-0003, Japan

TEL. [phone]

FAX. [phone]

URL : http://www.os-engines.co.jp

60090540 070501