
GT55
入力電圧
消費電流
出力電圧
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It is of vital importance, before attempting to
operate your engine, to read the general
'SAFETY INSTRUCTIONS AND WARNINGS'
section on pages 2-5 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.
Two stroke gasoline engine for airplanes
1
SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE
ABOUT THE ENGINE
ENGINE PARTS NAME
SILENCER / INSTALLATION
FUEL TANK & LINES
CARBURETOR WLA-2 PARTS NAME
CARBURETOR LINKAGE
IGNITION MODULE
PROPELLER
MIXING OF OIL
CONTENTS
RUNNING-IN / STARTING
NEEDLE ADJUSTMENTS
FLIGHT & MAINTENANCE
ENGINE EXPLODED VIEW
ENGINE PARTS LIST
CARBURETOR EXPLODED VIEW
CARBURETOR PARTS LIST
O.S. GENUINE PARTS & ACCESSORIES
ENGINE THREE VIEW DRAWINGS
MEMO
2-5
6
7
8
9
10
11-12
13-14
15-16
17
18-23
24-25
26-27
28
29
30
31
32
33
34

2
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.
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.
SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR
O.S. ENGINE
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
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.
Gasoline is poisonous. Do not allow it
come into contact with the eyes or mouth.
Always store it in a clearly marked
container in a cool and dark place and out
of the reach of children. There is a
possibility that it may damage your
health.
Gasoline is highly flammable. Keep it
away from an open flame, excessive heat,
sources of sparks, or anything else which
might cause it to ignite. Do not smoke or
allow anyone else to smoke near to it.
Carry out the mixing of the gasoline and
oil outdoors or in a well ventilated place
away from any source of fire to prevent
the possibility of a fire.
Refill the fuel tank only after the engine is
well cooled down, or there is a danger of
fire.
3
WARNINGS
Model engines generates 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
results in a serious burn.
Never operate your engine in an enclosed space.
Model engines, like automobile engines, exhaust
deadly carbon-monoxide. Run your engine only in
an open area.
Do not operate the engine nor model alone, or there
is a possibility of injury.
Any propeller requires utmost attention to handle.
Be sure to follow the instruction manual supplied
with a propeller.
This engine was designed for model aircraft.
Do not attempt to use it for any other purpose.
Start the engine only after installing it in the model.
Do not start the engine before installing it in the
model, or there is a possibility of injury.
Be sure to use an effective silencer (muffler).
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.
Mount the engine in your model securely, following
the manufacturers’ recommendations.
For their safety, keep all onlookers (especially small
children) well back (at least 10 meters) when
preparing your model for flight.
NOTES
Observe the laws and regulations in each country
and district concerning the usage, transportation
and storage of gasoline. Ask details at fire station in
each district.

4
When checking a spark plug with the power source
on, do not hold the plug, plug cap, high tension cord
nor grounding wire, or you will get a shock.
Install a top-quality propeller of the diameter and
pitch specified for the engine and aircraft.
Do not use a nylon propeller. It has the possibility of
flying apart due to strong centrifugal force caused
by high rpm.
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.
Install 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
washer and propeller installing screws using the
correct size wrench. Always check the tightness of
propeller installing screws and retighten them, if
necessary, before starting the engine. Also, check
the tightness of all the screws and nuts before
restarting the engine.
NOTES
Always check the throttle linkage.
If it is disconnected, throttle action becomes
uncontrollable, which may result in a serious
accident.
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.
Use an electric starter for this engine. The wearing
of safety glasses is also strongly recommended.
If you try hand starting, be sure to use a chicken
stick or heavy glove. Never attempt to start the
engine with a bare hand.
Be sure to carry out adjustments of the high speed
needle and slow speed needle after stopping the
engine.
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.
5
NOTES
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.
Switch off the ignition module to stop the engine or
fully close the throttle valve via the transmitter to
shut off the fuel supply. Otherwise there is a
possibility of injury.
Immediately after the engine is stopped, the engine
may start with a crank even when the igniter switch
is off. Do not crank the engine, or there is a
possibility of injury.
Be sure to install an externally operable switch for
the ignition system battery to stop the engine if it is
started unintentionally with the radio transmitter
turned off or there is the possibility of injury.
Connect the throttle linkage so that the engine can
be stopped via radio operation.

6
ABOUT THE ENGINE
This engine is designed for experienced fliers.
Beginners and newcomers should not use this
engine.
The engine unit, carburetor and igniter are
specially designed.
It offers broad power characteristics suitable for
sport flight as well as acro flight.
The large and dense cooling fins ensure
sufficient cooling against overheating.
The specially designed ignition module “IG-01” is
equipped with a micro computer and designed
not to operate at low rpm and run intermittently
when the battery voltage drops. It provide high
voltage for sure firing through the operating
range while utilizing a low current draw.
STANDARD ACCESSORIES
Spark Plug CM-6
入力電圧
消費電流
出力電圧
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Exhaust Gasket GT55
Ignition module Assembly (IG-01)
7
Propeller Retaining Screws
ENGINE PARTS NAME
Spark Plug
Cylinder Head
Crankcase
Cover Plate
Velocity Stack
Carburetor Complete WLA-2
Drive Spacer
Pilot Shaft
RPM Sensor
Propeller Washer
入力電圧
消費電流
出力電圧
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Sensor Leads
Battery Leads
Sensor Leads
High Tension Cord
Ground Wire

8
Be sure to use an effective silencer (muffler).
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.
Mount the engine in your model securely,
following the manufacturers’ recommendations.
Use a strong enough material for the mounting face of the
model, such as birch ply firewall of more than 8mm thick.
Make sure the mounting face of the model is flat. If it is
uneven, work on it to be flat. (When shims are added to
change the thrust angle, work on it to be flat.)
Engine mounting face has been high-precision machined
flat. Make sure mounting face of the model is also flat.
SILENCER / INSTALLATION
The GT55 does not come with a silencer. Select an
effective silencer from commercially available ones.
(Mounting bolt pattern is the same as most other makes of
the similar engine size.)
Use 5mm steel hex socket head bolts to install the engine.
(Do not use brass, soft steel nor aluminum screws,
because they are not strong enough.)
Also, use the Nord Lock Washers (optional extra) and
other anti-loosening washers or apply locking agent.
Be sure that there is sufficient air intake and outlet area on
the model for engine cooling to avoid overheating.
(Pay careful attention to the cooling since a gasoline
engine generates more heat than a glow engine.)
Secure at least a 30mm dia. area around the air intake of
the velocity stack so that the air intake will not be
restricted. (Cut out the cowling big enough if necessary.)
9
Use a tank designed for gasoline.
(Tanks designed for glow fuel use a rubber cap which is
deteriorated by gasoline.)
A 600cc tank will provide 13~14 minutes flight.
Install a commercially available gasoline fuel filter between
fuel tank and carburetor. (Clean the filter from time to time.)
For plumbing use TYGON F-4040 (Yellow color) or strong
nitrile rubber of more than 3mm ID and 6mm OD.
Replace tubing periodically as it becomes hardened.
(Replace tubing inside the fuel tank every six months.)
FUEL TANK & LINES
Use fuel line keepers at the end of the tubing to prevent at
from coming off.
This engine does not require a muffler pressurized fuel
system but be sure to provide an air vent.
Be sure to install an in-line fuel filter between the tank and
carburetor to prevent foreign matter in the tank from
entering the carburetor. Clean the filter periodically.
Be sure to use a gasoline resistant fuel tank cap.
Be sure to equip air vent pipe.
Be sure to use binding band to prevent from coming off.
Be sure to replace piping inside periodically.
To carburetor fuel inlet
Piping for re-fuelling
R

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Fuel Inlet
CARBURETOR WLA-2 PARTS NAME
Carburetor Body
High Speed Needle
Idle Speed Stop Screw
(No need to adjust. Factory adjusted.)
Slow Speed Needle
Air Vent Fitting
(No need to connect in normal use.)
Throttle Valve Lever
Choke Valve Lever
High Speed Stop Lever
High Speed
Stop Lever Retaining Screw
Idle Speed Stop Lever
Throttle Valve Lever
Retaining Screw
Spring Throttle Return
11
1.
2.
3.
4.
CARBURETOR LINKAGE
Remove the throttle lever retaining screw. (Pay attention
not to lose this screw because it is special size.) Also, be
careful not to remove the idle stop screw and return spring.
If they are removed accidentally, assemble them being
aware of the small notch.
Then, remove the opposite side high speed stop retaining
screw. (Pay attention not to lose this screw because it is
special size.) At this time, be careful not to remove the
high speed stop lever.
Then, install the throttle lever with the throttle lever
retaining screw.
Then, install the idle speed stop lever with the high speed
stop lever retaining screw.
Connect the throttle linkage so that the engine
can be stopped via radio operation.
Connect the throttle linkage so that the engine
can be stopped by radio operation in case of
unexpected starting, or there is a possibility of
injury.
Throttle lever can be installed either on right or
left. Here is a changing procedure.
When loosening and tightening each retaining screw, do
so with the throttle valve at mid position.
(If the throttle valve lever retaining screw is loosened or
tightened with the throttle valve fully opened or closed,
excessive force will be applied, which will results in
breaking the lever.)
NOTE

12
Before connecting the throttle linkage, make sure that the
throttle valve lever does not interfere with the bulkhead or
mount of the model when it is fully closed and opened.
Connect the throttle linkage so that clearance gap between
the idle stop and idle speed stop lever distance is
1~1.5mm (refer to the sketch shown below) when the
throttle stick on the transmitter is fully pulled down and the
throttle valve is fully closed as well as the trim lever on the
transmitter.
Connect linkage so that this
gap distance is 1~1.5mm.
(This is the idling position.)
Idle Stop
Idle Stop Lever
Connect the linkage so that the throttle valve is fully
opened when the throttle stick on the transmitter is fully
advanced. (Adjust the movement so that the pushrod does
not bind when the throttle valve is fully closed and fully
opened.)
Connect the linkage so that the servo arm and pushrod,
and throttle valve lever make a right angle when the
throttle stick on the transmitter is placed at mid position to
avoid differential action.
When changing the throttle valve lever and choke valve
lever direction, loosen and tighten each retaining screw
placing each lever at mid position. (If the throttle valve
lever retaining screw is loosened or tightened with the
throttle valve fully opened or closed, excessive force will
be applied, which will results in breaking the lever.)
There is no need to connect to the air vent fitting in normal
use. However, if the engine does not run steadily due to
pressure change caused by airflow in the cowl, connect
tubing to the inside of the fuselage.
13
Consumption current is 600mA/6,000rpm.
User a power source of more than 1000mA/h capacity.
For safety, with this ignition module the engine runs
intermittently over 5,000rpm when the power source
voltage drops below 3.8V.
With this intermittent running rpm do not increase the rpm
above mid speed, and land the model immediately.
The ignition module is set not to operate below 100rpm for
safety.
The voltage of power source is 4.8~7.4V (rated).
(Ni-Cd, Ni-H 4~6 cells, Li-Po, Li-Fe 2 cells)
When checking the spark plug with the power
source on, do not hold the plug, plug cap, high
tension cord nor grounding wire, or you will get a
shock.
Be sure to equip an externally-operable switch for
the ignition system battery to stop the engine if
started unexpectedly without switching on the
radio system, or there is a possibility of injury.
IGNITION MODULE
Major specifications
Installation
Install the ignition module taking sufficient anti-vibration
measures.
Install the ignition module at least 100mm away from the
engine and in a place where there is airflow so that engine
exhaust heat and radiation heat do not affect it's operation.
Do not share the power source with receiver and use a
separate power source.
Equip an ON/OFF switch between the ignition module and
its power source and install it in a place where can be
operated from outside the model.
Install the ignition module and its power source as far as
possible away from the servos and receiver power source.
Connect the ignition module grounding wire to the engine.
Make sure high the tension cord and grounding wire do not
touch the engine and cowl.
Install he plug cap on the plug securely.

14
Precautions
Do not disassemble the ignition module and plug cap.
(The ignition module is irreparable. Replace it when
necessary.)
Be careful not to mount the ignition module so that it can
be hit by water, gasoline or exhaust.
Avoid using the engine when the external temperature is
over 40 C.
Do not move the rpm sensor as it is placed at it's optimum
position, otherwise the engine will not run properly.
Do not pull on the high tension cord to remove the plug
cap, or the wire will break. Be sure to hold the plug cap to
remove it.
Do not connect nor disconnect the rpm sensor with the
ignition module on, or there is a possibility it will fire and
the engine start.
Check the ignition module for spark when installing the
plug cap on the plug and be careful about getting a shock.
Make sure there is no flammable material or gasoline
vapors near by that could ignite.
Do not turn the propeller with the ignition module on, or
there is a possibility the engine will start.
15
22x8
22x10 23x8 23x10
24x8 24x10
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.
Install a top-quality propeller of the diameter and
pitch specified for the engine and aircraft.
Do not use a nylon propeller. It has the possibility
of flying apart due to strong centrifugal force
caused by high rpm.
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.
PROPELLER
Use a wooden or a carbon fiber propeller.
Do not use a nylon 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 s starting point, refer to the props listed
in the table shown below. 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 high rpm or if a larger
diameter/lower pitch prop is used. Be well aware propeller
rotating arc is very large due to a large propeller used with
this engine. Carry out the needle adjustments only after
stopping the engine. Do not allow your face or hands to
come close to the rotating prop.
Type
Size (DxP)
Running-in
Sport/Acro/Scale
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 use any propeller which has become split, cracked
or nicked even very slightly, or received strong impact
even if no apparent damage is visible.

16
INSTLLATION OF PROPELLER
Install 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
washer and propeller retaining screws using the
correct size wrench. Always check the tightness
of propeller retaining screws and retighten them,
if necessary, before restarting the engine.
If the supplied retaining screws are too long due to a
thinner prop hub or too short due to a thicker prop hub
(cannot be screwed into the drive hub by more than
10mm), Use suitable length strong steel hex socket head
cap screws.
Install the propeller before the first flight of the day and
remove it after the day’s flight.
Make a habit of always checking the tightness of propeller
retaining screws making sure they are free of, damage or
rust before starting the engine. Replace the propeller
periodically (every 50 flights) even if it looks as ifs nothing
is wrong.
17
Use regular gasoline. (No need to use high octane
gasoline.)
Alcohol based glow fuel cannot be used in this engine.
Not only will the engine not work properly but the internal
carburetor plastic parts will be damaged.
Use high quality commercially available 2 stroke engine
oil.
Follow the oil manufacturer’s recommendations
concerning the mixture ratio of gasoline and oil. If there is
no recommendation, mix with a 30:1 ratio.
We have checked and approved the following oil mixture
ratio.
KLOTZ ModelLube (50:1), COSMO Cosmo Terra 2 cycle
(50:1), RED LINE Two-Stroke Racing Oil (40:1).
(This does not mean we guarantee the quality of these
oils.)
Follow the instructions in the running-in section concerning
the mixture for running-in.
With a gasoline engine, passages in the carburetor are
narrower than that of a glow engine, and therefore very
sensitive against foreign matter such as dust. It is
suggested to use optional accessory Super Filter L (Code
No. 72403050) when filling a tank in the model from a
container used for transportation or storing.
Gasoline is poisonous. Do not allow it to come
into contact with the eyes or mouth. Always store
it in a clearly marked container in a cool and dark
place out of the reach of children. There is a
possibility that it may damage your health.
Gasoline is 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.
Carry out mixing of gasoline and oil in a wellventilated and free of fire outdoor, place or there
is a possibility of fire.
Refill the models fuel tank only after the engine
has well cooled down, or there is a danger of fire.
Observe the laws and regulations in each country
and district concerning the usage, transportation
and storage of gasoline. Ask details at fire station
in each district.
MIXING OF OIL
R

18
Use a fuel with increased oil content and set the needle a
little on the rich side. Too rich a needle setting may cause
misfiring or erratic running due to fouling of the plug.
Use a 25:1 fuel/oil mixture if the particular brand of oil
states 30:1. If the oil states 50:1, use a 30:1 mix. Set the
high speed needle l00~200 below maximum rpm. The low
speed needle need not be richened.
No need to carry out running-in on a bench nor with the
model fixed. Just fly the model with the above mentioned
fuel and needle setting.
A total of 10 flights (5~6 litters fuel) are required.
Avoid prolonged full throttle running at initial stage, and
gradually extend the full throttle running time.
RUNNING-IN / STARTING
Always check the throttle linkage.
If it is disconnected, the engine becomes
uncontrollable, which may result in a serious
accident.
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.
Use an electric starter for this engine.
The wearing of safety glasses is also strongly
recommended.
If you try hand starting, be sure to use a chicken
stick or heavy glove. Never attempt to start the
engine with bare hand.
Be sure to carry out adjustments of the high
speed needle and slow speed needle after
stopping the engine.
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.
WARNING:
When ground running the engine, avoid dusty or sandy
locations. If dust or grit is drawn into the engine, this can
have a ruinous effect, drastically shortening engine life in
a matter of minutes.
19
1.
2.
3.
4.
5.
6.
7.
8.
9.
When starting the engine for the first time, set both the
high speed needle and the slow speed needle two turns
open from the fully closed position.
With this position both high and slow speed mixtures will
be rich.
If the settings are upset, come back to this setting and
adjust them according to procedure in the needle setting
section.
Since the carburetor points downward when the engine is
installed inverted, it becomes more difficult for the fuel to
reach the carburetor on priming (choking).
Therefore a heavier priming will be required.
Initial needle position
Starting by an electric starter
First starting of the day
Make sure the ignition switch is off.
Close the choke valve fully.
Set the throttle stick on the transmitter at bottom or 1/8
(2~3 clicks) advanced from the bottom.
Flip the propeller with a Chicken stick or gloved hand until
the fuel runs out of the carburetor. (In case of upright and
side installation, flip 7~8 more times after the fuel reaches
the carburetor.) Do not use an electric starter, or the
engine will be over-primed.
Open the choke valve fully.
Make sure the throttle stick is at the bottom or 1/8 (2~3)
advanced from the bottom.
Turn on the ignition switch.
Tell the helper and onlookers that you will start the engine
now and have the helper hold the model securely.
Apply the electric starter.

20
4.
5.
6.
7.
8.
9.
1.
2.
3.
4.
5.
Second and later starting of the day
Set the throttle stick on the transmitter at bottom or 1/8
(2~3 clicks) advanced from the bottom.
Make sure the choke valve is fully opened.
Turn on the ignition switch.
Tell the helper and onlookers that you will start the engine
now and have the helper hold the model securely.
Apply the electric starter.
Starting with a Chicken stick or gloved hand No.1
(Two different procedures are explained.)
(It is suggested to use an electric starter.)
First starting of the day
Flip the propeller until the fuel runs out of the carburetor,
then flip 3~4 times more (6~7 times in winter).
(In case of upright and side installation, flip 7~8 more time
after the fuel reaches the carburetor.)
Open the choke valve fully. With the throttle stick fully
open, flip 6~7 times to draw the fuel mixture into the
cylinder.
Set the throttle stick on the transmitter at bottom or 1/8
(2~3 clicks) advanced from the bottom.
Turn on the ignition switch.
Tell the helper and onlookers that you will start the engine
now and have the helper hold the model securely.
Usually the engine starts with 1~3 flips. If you have only
short runs or the engine does not start with more than 10
flips, most probably priming is not sufficient.
Repeat the procedure from the beginning.
Make sure the ignition switch is off.
Close the choke valve fully.
Fully advance the throttle stick on the transmitter.
1.
2.
3.
21
1.
2.
3.
4.
5.
4.
5.
6.
7.
8.
9.
1.
2.
3.
Make sure the ignition switch is off.
Close the choke valve fully.
Fully advance the throttle stick on the transmitter.
Flip a propeller 2~3 times (3~4 times in winter).
(In case of upright and side installation, flip 3~4 times.)
Open the choke valve fully. Flip the propeller 6~7 times to
draw the mixture into the cylinder with the throttle stick fully
advanced.
Set the throttle stick at bottom or 1/8 (2~3 clicks) advanced
from the bottom.
Turn on the ignition switch.
Tell the helper and onlookers that you will start the engine
now and have the helper to hold the model securely.
Flip the propeller with a Chicken stick or gloved hand to
start the engine.
Set the throttle stick on the transmitter at bottom or 1/8
(2~3 clicks) advanced from the bottom.
Make sure the choke valve is fully open.
Turn on the ignition switch.
Tell the helper and onlookers that you will start the engine
now and have the helper to hold the model securely.
Flip the propeller with a Chicken stick or gloved hand to
start the engine.
Note
If the engine does not start after more than 5 times repeat
the procedure, over-priming is suspected. Check whether
the plug is wet or not. If the plug is wet, replace it or wait
until it is dried. Then, flip the propeller swiftly (15~20
times) with the plug removed to eject the fuel in the
cylinder. Then, install the plug and repeat the starting
procedure.
Second and later starting of the day
Starting with a Chicken stick or gloved hand while the
engine is warm
Starting with a Chicken stick or gloved hand when the
engine is cold

22
1.
2.
4.
5.
6.
7.
8.
3.
Starting with a Chicken stick or gloved hand No.2
(It is suggested to use an electric starter.)
Fist starting of the day
Make sure the ignition switch is off.
Close the choke valve fully.
Set the throttle stick at bottom or 1/8 (2~3 clicks) advanced
from the bottom.
Flip the propeller until the fuel runs out of the carburetor,
then flip 3~4 times more (6~7 times in winter).
(In case of upright and side installation, flip 7~8 more time
after the fuel reached the carburetor.)
Open the choke valve fully.
Turn on the ignition switch.
Tell the helper and onlookers that you will start the engine
now and have the helper hold the model securely.
Flip the propeller with a Chicken stick or gloved hand to
start the engine. Usually the engine will start with 5~6 flips.
If you have only short runs or the engine does not start
with more than 15 flips, most probably the priming is not
sufficient. Repeat the procedure again.
Note
If the engine does not start after more than 5 times repeat
the procedure, over-priming is suspected.
Check whether the plug is wet or not. If the plug is wet,
replace it or wait until it is dried.
Then, flip the propeller swiftly (15~20 times) with the plug
removed to eject the fuel in the cylinder.
Then, install the plug and repeat the starting procedure.
23
1.
2.
4.
5.
6.
7.
8.
3.
Set the throttle stick at bottom or 1/8 (2~3 clicks) advanced
from the bottom.
Make sure the choke valve is fully open.
Turn on the ignition switch.
Tell the helper and onlookers that you will start the engine
now and have the helper hold the model securely.
Flip the propeller to start the engine.
Second and later starting of the day
Starting with a Chicken stick or gloved hand while the
engine is warm
1.
2.
4.
5.
3.
Make sure the ignition switch is off.
Close the choke valve fully.
Set the throttle stick at bottom or 1/8 (2~3 clicks) advanced
from the bottom.
Flip the propeller 2~3 times (3~4 times in winter).
Open the choke valve fully.
Turn on the ignition switch.
Tell the helper and onlookers that you will start the engine
now and have the helper hold the model securely.
Flip the propeller to start the engine.
Starting with a Chicken stick or gloved hand when the
engine is cold

24
1/4
1/2
3/4
6.
7.
8.
1.
2.
4.
5.
3.
Start the engine. Open the throttle valve slowly until fully
open and run the engine for 10 seconds to warm the
engine.
Set the throttle stick 3 clicks advanced from the bottom and
measure rpm with a tachometer and write it down.
Close the slow speed needle approx. 30 degrees and
measure rpm with a tachometer and write it down. (Be sure
to adjust the slow needle only after stopping the engine.)
Repeat step 4. to locate the slow speed needle position
where maximum rpm is achieved. Open it approx. 30
degrees from this position. This is the basic slow needle
position.
Open the throttle valve fully and measure rpm with a
tachometer and write it down.
Close the high needle approx. 30 degrees and measure
rpm and write it down. (Be sure to adjust the high needle
only after stopping the engine.)
Repeat step 7. to locate the high needle position where
maximum rpm is achieved. Open it approx. 30 degrees
from this position. This is the basic high needle position.
Set the throttle trim on the transmitter so that the idle rpm is
approx. 2,000
(approx. 1,600rpm when idle down function is used).
NEEDLE ADJUSTMENTS
The slow speed needle is effective through the high
speed range, while the high speed needle is not effective
in the low speed range. Both needles are effective in the
mid speed range, while the slow speed needle is the most
effective. (Refer to the diagram below.)
Fuel Flow
High Needle
Effective Range
Slow Needle Effective Range
Throttle Opening
Fully open
More
Less
Carry out the needle settings as follows.
Adjustment on the ground
Set both needles at two turns open from the fully closed
position.
9.
25
10.
11.
12.
14.
15.
16.
13.
Warm the engine for 10 seconds with the throttle fully
open, then idle the engine for 5 seconds, then quickly
open the throttle fully. Make sure the engine does not
respond sluggishly to increase rpm nor hesitates before
picking up speed or even ceases firing.
If the engine responds sluggishly to increase rpm, the
mixture is too rich due to the slow speed needle being
open too far. Close the slow speed needle approx. 15
degrees. Repeat this procedure until the engine
accelerates smoothly. (Be sure to adjust the slow speed
needle only after stopping the engine.)
If the engine hesitates before picking up speed or ceases
firing, the mixture is too lean due to the slow speed needle
being open too far. Open the needle approx. 15 degrees.
Repeat this procedure until the engine accelerates
smoothly. (Be sure to adjust the slow speed needle only
after stopping the engine.)
Adjustment with flight
If the rpm drops or the exhaust sound weakens when
vertically climbing from level flight with full throttle, the
mixture is too lean. Land the model and open the high
speed needle approx. 15 degrees. Repeat this procedure
until the engine sound is smooth.
If, on the other hand, exhaust sound is irregular when
vertically climbing from level flight, the mixture is too rich .
Land the model and close the high speed needle approx.
15 degrees. Repeat this procedure until the sound in level
flight is steady.
If the power drops gradually or exhaust sound weakens
(overheating symptom), when performing torque roll and
hovering, the mixture is too lean. Land the model and
open the slow speed needle approx. 15 degrees. Repeat
this procedure until power remains steady.
If the above symptom is not detected with prolonged
torque roll and hovering but sluggish to increased rpm
when the throttle is fully opened abruptly, the mixture is
too rich. Land the model and close the slow speed needle
approx. 15 degrees until sluggish rpm increase
disappears.
Note
Generally, a gasoline engine is sensitive to a lean mixture
compared with a glow engine, and will stop without
warning hesitation and stops with overheating.
It is recommended that the engine be run with a slightly
richer mixture.

26
When the engine is started, make sure the radio control
system works normally (distance test).
Engine does not run erratic with full throttle.
Idling is stable.
Responds positively to the throttle operation.
Warm-up is finished.
FLIGHT & MAINTENANCE
Checking prior to flight
Warm-up is required as with full size aircraft and car engines.
Take off the model after warming the engine for approx. 10
seconds with full throttle.
Precautions in flight
A slight engine rpm increase and decrease delay is
normal. Abrupt throttle operation will the cause engine to
quit. Move throttle smoothly.
Due to the construction of the carburetor, 70~80% of
maximum power develops with half throttle.
If you feel uneasy with this, adjust with transmitter
function (exponential and throttle curve, etc.) or
differential of throttle linkage.
Maintenance after the day’s flights
Please pay attention to the matter described below to
ensure that your engine serves you well in regard to
performance, reliability and long life.
Check the tightening of each screw, especially engine
installing screws and silencer installing screws each
time. Also, for the first several flights, tighten the screws
after each flight.
As previously mentioned, it is vitally important to avoid
operating the engine in conditions where dust,
distributed 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 foreign matter in the fuel
container from entering the fuel tank. O.S. Super Filter
(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.
Clean these filters periodically.
27
If these precautions are neglected, restrictions of fuel
flow may cause the engine to cut out, or the fuel/air
mixture to become too lean causing the engine to
overheat.
With a gasoline engine rust hardly occurs. Check the
exterior to make sure there is nothing wrong and wipe
off any oil res.
Fill the carburetor with fuel at the conclusion of a day's
flying. (Pay careful attention to fire and ignition source
when carrying and storing the model.)
If the engine is stored without filling the carburetor, with
fuel the inside parts will dry out and not work properly at
the next running. If the engine quits out of fuel, refill the
carburetor with fuel.
When the engine is not to be used for a long period
(more than a year), remove the engine from the model,
clean the outside then remove the carburetor, and plug
all tubing. Clean inside the engine by rotating the
crankshaft with the engine immersed in container filled
with gasoline.
Also use gasoline to clean the outside of the carburetor.
Do not use kerosene, or the inside parts will be
damaged. Clean the outside only because the inside
parts are sensitive to foreign matter.
After cleaning the engine, dry it well then inject a small
quantity of oil used to mix fuel and rotate the crankshaft
several times to distribute the oil well inside the engine.
Finally reassemble the engine and store it in a dry place
after inserting it in a heavy vinyl bag.

28
ENGINE EXPLODED VIEW
Type of screw
C...Cap Screw
入力電圧
消費電流
出力電圧
Inpu
t
vo
ltag
e
Co
nsum
ption current
O
utput
vo
lta
ge
DC
4.8V
-7.6
V
600mA/60
00r
pm/4.8
V
20KV/6000r
pm/4.8
V
5
C.M4x20
C.M5x50
1
1-1
2
3
4
6
7
8
9
10
11
12-1
12
C.M5x45
13
14
16
15-1
15-2
15
17
18-1
18
19
20
21
22
C.M5x15
C.M3x8
M3
79871420
79871515
79871545
79871550
M4x20
M5x15
M5x45
M5x50
CAP SCREW SETS
(10pcs./sets)
Code No.
Size
Cylinder Head Retaining Screw (6pcs.)
Cover Plate Retaining Screw (4pcs.)
Propeller Washer Retaining Screw (4pcs.)
Velocity Stack Retaining Screw (2pcs.)
Pcs. used in an engine
29
The specifications are subject to alteration for improvement without notice.
1
1-1
2345678
9
101112
12-1
131415
15-1
15-2
161718
18-1
192021
22
29704000
29714100
29703100
29703400
29703200
29706000
29717000
29705000
29781300
29781000
29781110
29781500
29701200
29701210
29709000
29702100
29708000
29708100
29708200
29730000
29701000
29701300
29701310
29731000
29702000
29714200
29707000
74002000
74002200
71669000
29714300
Description
Code No.No.
Cylinder Head
Head Gasket
Cylinder Liner
Piston Ring
Piston
Piston Pin
Piston Pin Retainer
Connecting Rod
Velocity Stack
Carburetor Complete (WLA-2)
Carburetor Insulater
Carburetor Gasket Set
Rotation Sensor
Rotation Sensor Retaining Screw Set
Propeller Washer
Pilot Shaft
Drive Spacer
Taper Collet
Pararel Key
Ball Bearing (F)
Crankcase
Crankcase Plug
"O" Ring
Ball Bearing (R)
Crankshaft
Cover Gasket
Cover Plate
Ignition Module (IG-01)
Plug Cap Set
Spark Plug CM-6
Exhaust Gasket GT55
ENGINE PARTS LIST

30
Type of screw
N...Round Head Screw
CARBURETOR EXPLODED VIEW
10
1
N4-40x5
2
3
4
5
6
7
8
9
9-1
11
12
13
4-4x40
12
4-4x40
12
4-4x40
14
15
16
17
18
19
20
19-1
N4-40x5
21
22
23
24
25
24-1
24-2
24-3
24-4
24-5
24-6
26
27
28
31
The specifications are subject to alteration for improvement without notice.
CARBURETOR PARTS LIST
1
2
3
4
5
6
7
8
9
9-1
10
11
12
13
14
15
16
17
18
19
19-1
29781340
29781330
29781460
29781450
29781430
29781440
29781410
29781420
29781360
29781350
29781310
29781320
29781570
29781550
29781510
29781560
29781520
29781530
29781540
29781370
29781350
Description
Code No.
No.
Spring-Choke Friction
Ball
Plug-Friction
Screw-Idle Speed
Needle-High Speed
Spring-Needle (H) ADJ.
Needle-Idle
Spring-Needle ADJ.
Choke Arm Assy
N4-40x5 Retaining Screw
Shaft-Choke
Valve-Choke
4-40x4 Retaining Screw
Lever-Outer
Shaft-Throttle
Ring-Retaining
Valve-Throttle
Spring-Throttle Return
Link-Throttle
Throttle Arm Assy
N4-40x5 Retaining Screw
20
21
22
23
24
24-1
24-2
24-3
24-4
24-5
24-6
25
26
27
28
29781020
29781030
29781040
29781050
29781270
29781060
29781210
29781220
29781230
29781240
29781250
29781120
29781130
29781140
29781070
Description
Code No.
No.
Gasket Passage
Plate-Passage
Gasket-Pump
Diaphragm-Pump
Body Assembly Pump
Screen-Inlet
Spring-Metering
Valve Inlet Needle
Pin-Metering Lever
Lever-Metering
Screw-Metering
Gasket-Metering Diaphragm
Diaphragm Assembly-Metering
Cover Assembly-Metering (W/Nipple)
Carb. Assemble Screw

32
(72403050)
(79870050)
(55500004)
(71531010)
SUPER FILTER (L
)
O.S. GENUINE PARTS & ACCESSORIES
M5
BLIND NUT (10pcs.)
LOCK WASHER (10sets)
M5
NON-BUBBLE WEIGHT
(S)
(72403051)
SUPER FILTER (S
)
The specifications are subject to alteration for improvement without notice.
33
40.5
40
47.4
47.4
74.6
2020
2-M5
37.5
112.5
150
139.2
75
40
35
41.2
33
33
66
39 39
78
30
Dimensions (mm)
THREE VIEW DRAWING
Specifications
Displacement
Bore
Stroke
PracticalR.P.M.
Output
Weight
(Engine)
(Ignition Module)
54.93 cc / 3.352 cu.in.
41.2 mm / 1.62 in.
41.2 mm / 1.62 in.
1,500-8,000 r.p.m.
5.5 ps / 7,000r.p.m.
1580 g / 55.7 oz.
140 g / 4.94 oz.

60092290 021002
C
Copyright 2009 by O.S.Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan.
TEL. (06) 6702-0225
FAX. (06) 6704-2722
6-15 3-Chome Imagawa Higashisumiyoshi-ku
Osaka 546-0003, Japan
URL : http://www.os-engines.co.jp