O.S. engine MaX-37SZ-HRING User manual

It is of vital importance, before attempting to operate
your engine, to read the general 'SAFETY
INSTRUCTIONS AND WARNINGS' section on
pages 2-5 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 model, radio control equipment, etc., are
accessible for checking at the same time.
1
2-5
6-7
8-9
10-11
16
20-23
29
36-37
38-39
40
24-28
17
30-31
32-35
12-15
18-19
41
42
CONTENTS
SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE
NOTES ON INSTALLING
COOLING-FAN AND CLUTCH
NOTES WHEN APPLYING AN ELECTRIC STARTER,
INSTALLATION OF THROTTLE SERVO
INTRODUCTION, ENGINE PARTS NAME 
BEFORE STARTING,
INSTALLATION OF THE ENGINE
INSTALLATION OF THE STANDARD ACCESSORIES
GLOWPLUGS
CARBURETOR CONTROLS
STARTING, RUNNING-IN ("Breakingin")
ADJUSTMENT
ADJUSTMENT CHART
CARE AND MAINTENANCE
TROUBLE SHOOTING
ENGINE EXPLODED VIEW & PARTS LIST
CARBURETOR EXPLODED VIEW & PARTS LIST
O.S. GENUINE PARTS & ACCESSORIES
THREE VIEW DRAWING
MEMO

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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.
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.
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 NOTES
These cover events which
might involve serious (in
extreme circumstances, even
fatal) injury.
These cover the many other
possibilities, generally less obvious
sources of danger, but which, under
certain circumstances, may also
cause damage or injury.
3
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WARNINGS
••
•
•
•
Never touch, or allow any
object to come into contact
with, the rotating parts.
Model engine fuel is poison-
ous. 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.
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.
Never operate your engine in an en-
closed space. Model engines, like auto-
mobile engines, exhaust deadly carbon-
monoxide. Run your engine only in an
open area.

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4
NOTES
•
•
•
•
•
This engine was designed for model
helicopters. Do not attempt to use it for any
other purpose.
Mount the engine in your model securely, fol-
lowing the manufacturers' recommendations,
using appropriate screws and locknuts.
Install an effective silencer (muffler). Frequent
close exposure to a noisy exhaust (especially
in the case of the more powerful high-speed
engines) may eventually impair your hearing
and such noise is also likely to cause
annoyance to others over a wide area.
Check the linkage to the throttle arm before
each flight.
Avoid sudden high r.p.m. immediately after the
engine is started, as the clutch will engage and
you may be struck by the rotor.
•
•
After starting the engine, carry out any needle-
valve readjustments after stopping the rotor by
closing the throttle to the lowest r.p.m..
Stop the engine before attempting to make
other adjustments to the carburetor.
Use an electric starter. The wearing of safety
glasses is also strongly recommended.
Press the rotor head down securely.
Take care that the glow plug clip or battery
leads do not come into contact with rotating
parts.
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.
•
•
5
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NOTES
•
•
•
Take care that loose clothing (ties, shirt sleeves,
scarves etc.) do not come into contact with the
rotor. Do not carry loose objects (such as pen-
cils, screwdrivers, etc.) in a shirt pocket from
where they could fall through the rotor disc.
For their safety, keep all onlookers (especially
small children) well back (at least 20 feet or 6
metres) 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.
Hold the rotor securely and keep well clear of
spectators.
Warning! lmmediately after a glowplug-ignition
engine has been run and is still warm,
conditions sometimes exist whereby it is just
possible for the engine to restart when turned
over WITHOUT the glowplug battery being
reconnected. Remember this if you wish to
avoid the risk of accidents.

6
Notes on installing cooling fan and clutch
Do not use a tool which locks piston
when installing a cooling-fan and
clutch, or top of the piston may be
damaged. Also, do not insert a
screw driver or the similar into the
exhaust port.
It is recommended to use Crankshaft
Clamp 37 (Code No.71530600) available
as an optional tool.
7
Do not grip the engine mounting
beams with a vise, or the crankcase
will be distorted which will result in
engine breaking.
Vise
Beam Mount
Notes on installing cooling fan and clutch

8
NOTES WHEN APPLYING AN ELECTRIC STARTER
Because of this initial tightness, a
standard electric starter may have
difficulty in rotating the engine when
cold, before it has been adequately
run-in. In this case, use a high-torque
type starter.
Do not over-prime. This could cause a
hydraulic lock and damage the engine
on application of the electric starter.
If over-primed, remove glowplug, close
needle-valve and apply starter to pump
out surplus fuel. Cover the head with a
rag to prevent pumped out fuel from
getting into your eyes.
9
F
J J
F
28
34
27 33
A
B
90°
90°
A=B
Linking the throttle servo to the carburetor
Link the throttle servo to the carburetor using the throttle lever supplied.
Throttle control rod A and B should be equal length. Set the linkage so that
the servo output lever and throttle lever are parallel when the throttle stick on
the transmitter is at middle position. Installing hole intervals on the F lever and
on the J lever are different. Decide the lever to use according to the servo used.
Be sure to cut off another lever to avoid any interference.

10
INTRODUCTION
Throttle lever is not installed on
the carburetor when the engine
leaves the factory.
Install it before using the engine.
NOTE
STANDARD ACCESSOIES
Glow Plug No.8
Throttle Lever Assembly
This is a high performance engine
designed for small-sized radio-
controlled helicopters.
Since the mounting bolt pattern of the
engine as well as silencer is the same as
those of the 32SX-H, it can be directly
replaced with the 32SX-H and most of
other 32-39 size engines. This powerful
engine is suitable for sport flight as well
as 3D flight.
With some models, needle interferes the
body and working on the body to avoid
this would be required.
Instruction manual
11
ENGINE PARTS NAME
Needle Valve
Fuel Inlet
Mixture Control Valve
Throttle Lever
Rotor Guide Screw
Carburetor Gasket
Heatsink Head
Carburetor
Type 20M
Crankshaft
Propeller nut
Crankcase
Glowplug
Beam Mount
Cover Plate
Thrust Washer

12
Items necessary for starting
Tools, accessories, etc.The following items are
necessary for operating the engine.
Battery leads
Glowplug battery
The power source for heating the glowplug may be
either a large heavy-duty 1.5volt dry cell, Ni-cd battery
or glowplug Igniter.
1.5 volt dry cell
These are used to conduct current
from the battery to the glowplug.
Basically, two leads, with clips, are
required, but, for greater conve-
nience, twin leads with special
glowplug connectors, as shown on
the right, are commercially available.
Battery leads
glowplug Igniter
Make sure glowplug element
glows bright red inside room
or shadow.
Battery leads
In case of 1.5volt dry cell
12V Battery
Starter
Electric starter and starter
battery
An electric starter is recom-
mended for starting.
Hexagon starting shaft
This shaft mounted on an
electric starting motor is driven
into the shaft cup to turn the
engine.
BEFORE STARTING
13
Select, by practical tests, the most suitable fuel from among
the best quality fuels available in your country for helicopter
use. For the best throttle response, a fuel containing 10% to
30% nitromethane is preferable. Lubricants may be either
castor-oil or a suitable synthetic oil (or a blend of both)
provided that they are always of top quality. For consistent
performance and long engine life, it is essential to use fuel
containing AT LEAST 18% lubricant by
volume. Some fuels containing coloring
additives tend to deterriorate and may
adversely affect running qualities. If in
doubt compare to a fuel known to be good.
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.
Reminder!
Fuel
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.
Alternatively, one of the purpose-made
manual or electric fuel pumps may be
used to transfer fuel directly from your
fuel container to the fuel tank.
Manual
Electric
Install a filter to the outlet tube of your
refueling container to prevent entry of
foreign matter into fuel tank. O.S. ‘Super
Filters’ (large and small) are available as
optional extras.
O.S. Super Filter (Fuel Can Filter)
It is recommended to install a good in-
line filter between the fuel tank and
carburetor to prevent entry of foreign
matter from getting into the carburetor.
Fuel Filter
Heatproof silicone tubing of approx.
5mm o.d. and 2.5mm i.d. is required
for the connection between the fuel
tank and engine.
Fuel Pump
Silicone Fuel Line

14
TOOLS
Screwdriver
Necessary for engine installation.
1.5mm, 2mm, 2.5mm, 3mm
Necessary for carburetor adjustments.
No.1, No.2, etc
Phillips Screwdriver
No.1, No.2, etc.
Socket Drivers
5mm, 5.5mm, 7mm
Hex Drivers
8mm
Recommended for easy removal and replacement of
the angled and recessed glowplug, the O.S.Long
Socket Wrench incorporates a special grip.
End Wrenches
8mm, 13mm, 14mm, etc.
Needle Nose Pliers
Long Socket Wrench With Plug Grip
15
The under-surfaces of all O.S. engine beam
mounting lugs are precision machined flat and
exactyly parallel to the engine's horizontal axis. It is
essential that the engine mounts in the model are
also accurately made and aligned. If they are not,
they will cause stress and distortion within the engine
itself, probably resulting in loss of performance and
internal damage.
The recommended screws for securing the engine to
the engine mounts in the model are 3mm or 4-40
steel Allen type. It is also advisable to use lock
washers or LOCTITE to prevent nuts from loosening.
Front view
CORRECT
Side view
Top surfaces are in the same plane.
Re-align the surfaces as necessary
INCORRECT
Top surfaces are not
in the same plane. Top surfaces are not in the
same plane.
Engine does not rest firmly.
Make sure that only the under-
surfaces of the engine’s mounting
lugs are in contact with the engine
mount.
INSTALLATION OF THE ENGINE
Make sure that only the under-surfaces of the engine’s
mounting lugs are in contact with the engine mount.
Please note that crankcase volume of the 37SZ-H is a
little larger than the 32SX-H’s. If the crankcase body
touches the mount, chamfer the edges of the mount.

16
INSTALLING THE GLOWPLUG
Install washer on glowplug and insert carefully into
Heatsink-head, making sure that it is not cross-
threaded before tightening firmly.
Glow plug
Washer
Throttle lever is not installed on the carburetor
when the engine leaves the factory.
Install it before using the engine referring to the
sketch below.
INSTALLATION OF THE THROTTLE LEVER
INSTALLATION OF THE STANDARD ACCESSORIES
Throttle Lever
Retaining Screw
Washer
17
GLOWPLUG
The role of the glowplug
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.
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 become
cooler and ignition is retarded.
Apart from when actually burned out, a plug may
need to be replaced because it no longer delivers its
best performance, such as when:
When to replace the glowplug
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.
Since the glowplug and fuel combination
used may have a marked effect on
performance and reliability, it would be
worthwhile to experiment with different
plug types. Recommended O.S. plugs are
No.8, No.7 and No.10 (Former A5) .
Carefully install plug finger-tight, before
final tightening with the correct size plug
wrench.

18
CARBURETOR CONTROLS
With a fixed-wing model, power failure is rarely a
serious threat to the safety of the aircraft since it can
usually glide down to a safe landing. In a helicopter,
on the other hand, it is vitally imporant that the engine
keeps running and that there is a quick and reliable
response to the throttle in order to ensure safe ascent
and descent of the model.
The Needle Valve:
When set to produce maximum power at full throttle,
this establishes the basic fuel/air mixture strength.
This is then maintained by the carburetor's
automatic mixture control system to cover the
engine's requirements at reduced throttle settings.
The Mixture Control Valve
For adjusting the mixture strength at part-throttle
and idling speeds, to obtain steady idling and
smooth acceleration to medium speeds. The Mixture
Control Valve has been factory set for the
approximate best result. First, run the engine as
received, and re-adjust the Mixture Control Valve
only when necessary.
Two adjustable controls are provided on this carburetor.
Needle Valve
MIxture Control Valve
19
REALIGNMENT OF MIXTURE CONTROL VALVE
In the course of making carburetor adjustments, it is
just possible that the Mixture Control Valve may be
inadvertently screwed in or out too far and thereby
moved beyond its effective adjustment range.
Its basic setting can be reestablished as follows :
Mixture Control Valve
Carburetor Body
First rotate the Mixture
Control Valve until its
slotted head is flush with
the carburetor body.
Then screw the valve in
exactly 1 turn. This is the
standard position.
0.5mm
As shown in the sketch, the carburetor has graduation
marks. When the triangle mark on the carburetor rotor
meets the most right mark, throttle is fully closed.
When the triangle mark meets the top mark, throttle is
fully open. The range is approximately 80 degrees. You
may use other three marks as the reference marking of
throttle opening to your preference when hovering.
WARNING!
Never try to check the triangle mark position while
the engine is running and rotor is rotating, or you
may be hit by rotating rotor which results in serious
injury. Stop the engine and rotor before checking
the triangle mark position.
Carburetor Rotor
Carburetor Body
Fully closed position
Fully opened position Approx.
GRADUATIONS ON THE CARBURETOR BODY

20
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Be sure to use an electric starter to start
the engine.
Fill the fuel tank with fuel. When filled, prevent the
fuel from flowing into the carburetor with a
commercially available fuel stopper, etc. Release
the stopper before starting the engine.
1.
2.
Starting procedure is as follows:
WARNING
When checking the plug element hold the plug
with tools, such as pliers, etc.
Do not hold near your face or the fuel remaining
in the filament may burn you.
Glow Plug Igniter
Pliers
Element glows when energized.
Replace the plug when the
element does not glow or is
burnt out.
Make sure that plug element glows red, and install
the plug in the cylinder head.
Never fail to check the tightness of screws
and nuts, especially engine mounting and
moving parts (e.g. throttle lever).
Be sure to use a muffler pressurized fuel feed.
Use the same fuel as you intend to employ for
actual operation of your model.
STARTING
21
Close
Open
1.
2.
3.
Opening and closing of the Needle-Valve
Turn the needle clockwise to
close the needle-valve, and turn
the needle counter-clockwise to
open the needle-valve as shown
in the sketch.
Opening the needle-valve
Firstly, turn the needle clockwise slowly until it
stops. The position it stops is the fully closed
position of the needle-valve. Make note this
position for reference..
Open the needle-valve 1.5 turns.
Preparation of the starter
Install the starting shaft to the
starter securely. Poor installation
swings the starting shaft, which is
dangerous.
4.
5.
6.
Checking the rotating direction of the starter
Make sure that the starter rotates
to the direction shown in the
sketch. If the direction is reverse,
reverse the leads on battery.
Inserting the starter shaft
Insert the starting shaft into the
shaft cup securely.
Priming
Without heating the glowplug, open the throttle a
little from the idle position. Turn the engine using
the starter until the fuel is seen to reach carburetor.

22
Preparation of starting
Make sure that the transmitter
throttle stick is at the fully closed
position and the throttle trim at
center position, and make sure that
idle-up switch on the transmitter is
off. Hold the rotor head by hand so
that rotor cannot rotate when the
engine is Started. Also, steady the
model with a foot on the landing-
gear skid.
7.
In case the engine does not stop.
Hold the rotor head, and pinch the silicone tube to
stop the fuel supply. If it still does not stop, pull off the
fuel tubing from the carburetor. It is necessary to
readjust the throttle linkage so that the carburetor
rotor is fully closed when the throttle stick and throttle
trim on the transmitter are fully pulled down.
Stopping the engine
Fully pull down the throttle trim on the transmitter.
Starting
Connect the battery to the glowplug and start the
engine by applying the starter. When started,
switch off the starter and withdraw the starting
shaft after making sure the rotation of the starter
shaft stops.
8.
9.
Note:
Make sure that the throttle linkage is made so that
the throttle is fully closed when the throttle lever
as well as trim lever on the transmitter are fully
pulled down.
NOTE:
If the throttle response is poor or the engine
stops due to a temporarily over-rich mixture im-
mediately after the engine is started, pinch the
fuel line for one or two seconds until the engine
r.p.m. increase and the engine runs steadily.
Reminder!
Never touch, or allow any object to come
into contact with, the rotating rotor.
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23
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 allows the working parts to mate together under
load at operating temperature.
However, because O.S. engines are made with the
aid of the finest modern precision machinely and from
the best and most suitable materrials, only a very
short and simple running-in procedure is required and
can be carried out with the engine installed in the
model.
For the first few flights with a new engine i.e. while
the engine is being run-in set the needle-valve for a
slightly rich mixture not excessively rich as this may
result in poor throttle response and cause the engine
to stop.
About one half turn open from the nomal setting will
usually suffice.
RUNNING-IN ("Breaking-in")

24
ADJUSTMENT
A
The following adjustments are approximately correct
when using a fuel containing 18-25% lubricant and
10-30% nitromethane.
Bear in mind that fuels containing relatively large
percentages of power-boosting nitromethane operate
at richer mixture settings than are needed for mild
fuels and will, therefore, require the Needle Valve to
be readjusted accordingly. The type and percentage
of lubricant used is also a factor here, as noted later
in these instructions.
This carburetor is not equipped with a throttle
stop screw. Instead, idle speed is adjusted by
means of the throttle trim lever on the trans-
mitter.
This enables the full r.p.m. range, from idling to full
power, to be controlled by the throttle stick, and
then allows the engine to be stopped, from the
transmitter, by closing the throttle completely with
the trim lever.
As a safety measure, first check the transmitter
controls, including the throttle stick and trim lever
positions, and hold the main rotor securely before
starting the engine.
B
Set up the throttle linkage as follows:
With the transmitter throttle trim lever fully
retarded, adjust the throttle servo linkage so that
the throttle rotor is (a) fully open when the
transmitter throttle stick is fully advanced and (b)
fully closed (i.e. engine stopped) when the stick is
fully retarded. The idle speed is then set by
advancing the throttle trim lever to the point where
the engine runs, steadily and reliably,at the
desired idle speed.
25
lf, at this time, the engine is slow to pick up and
produces an excess of exhaust smoke, the mixture
is too rich. Correct this condition by turning the
Mixture Control Valve clockwise. lf the mixture is
extremely rich, engine rpm will become unstable :
opening the throttle will produce a great deal of
smoke and rpm may drop suddenly or the engine
may stop. This condition may also be initiated by
an excessively prolonged warming-up period.
lf, on the other hand, the mixture is too Iean, this
wiIl be indicated by a marked lack of exhaust
smoke and a tendency for the engine to cut out
when the throttle is opened. ln this case, turn the
Mixture Control Valve counter-clockwise to enrich
the mixture.
D
E
Hover the model and actuate the throttle to
observe response over the medium speed range.
lf the engine smokes excessiveIy and throttle
response is poor, the mixture is too rich ; in which
case, land the model and turn the Needle Valve
clockwise. Do not close the NeedIe Valve too
much, keeping it a little on the rich side at this
stage.
lf, on the other hand, hovering is not stable and
response to the throttIe is over-sensitive, or if the
engine tends to overheat, this indicates that the
mixture is too lean and should be corrected by
turning the Needle Valve counter-clockwise.
H
I
Warm the engine by allowing it to idle for about 30
seconds. If the engine stops, advance the throttle
trim lever slightly to increase the idle rpm. Then
open the throttle sufficiently to 'float' the model
above the ground.
CTurn the Mixture Control Valve 15 degrees at a
time.
Having provisionally set the idle mixture, the next
step is to adjust the mixture for hovering flight.
F
G

26
LNow adjust the Needle Valve to achieve the best
performance when the model is flying at full
throttle. lf, at full throttle, acceleration is poor, the
exhaust unduly smoky and the model fails to reach
expected straight line speed, the mixture is too rich
and the Needle Valve setting will need to be
reduced. lf, however, after smoothly acceIerating
to satisfactory high-speed straight and level flight,
power is lost when the model is puIled up into a
climb, the mixture is too lean. ln this case, land the
model immediately and readjust Needle Valve to a
richer setting.
M
NFor helicopters, good throttle response at medium
r.p.m. (e.g.hovering speeds) is most important,
since this is a power range widely used in
helicopter flight. The optimum fuel/air mixture
strength at medium speeds is dependent on
obtaining balanced adjustment of both the Needle
Valve and the Mixture Controlof both the Needle
Valve and the Mixture Control Valve. lf both
controls are already at their optimum setting, some
modification to these settings may be necessary to
achieve satisfactory mid-range throttle response,
but such readjustments should onIy be made
within the range where idle reliability and high-
speed performance are not unduly compromised.
Readjustments should therefore be carried out as
follows:
After about 10 seconds of idling, open the throttle
to 'float' the model. lf the transition is smooth, the
idle mixture is O.K. If the symptoms of either rich or
Iean running are observed, readjust the Mixture
Control Screw accordingly.
K
When satisfactory hovering flight has been
achieved, land the modeI again and re-check the
engine's idle qualities.
JNow re-check hovering performance and, if
necessary, fine-tune the mixture for hovering flight.
27
lf, on the other hand, the response to mid-range
throttle movement is too sensitive (indicating a lean
mid-range mixture), turn the Needle Valve 2 or 3
clicks counter-clockwise or turn the Mixture Control
Valve 1-3 degrees counter-clockwise.
Throttle response at hovering speeds is aIso
affected by the reIationship of the main rotor pitch
angle to throttle opening. If the optimum mid-range
throttle response cannot be obtained by the
carburettor adjustments described above, try
adjusting the helicopter's pitch control
characteristics.
Q
P
Olf the mid-range throttle response is not rapid and
positive (indicating a rich mid-range mixture), turn
the Needle Valve 2 or 3 clicks clockwise, or turn the
Mixture Control Valve 1-3 degrees cIockwise.

28
CARBURETOR CLEANLINESS
SUBSEQUENT READJUSTMENTS
Once the engine has been run-in and the carburetor
controls properly set up, it should be unnecessary to
alter the mixture settings, except to make minor
adjustments to the Needle Valve occasionally, to take
account of variations in climatic condisitions.
The use of a different fuel, however, particularly one
containing more, or less, nitromethane and / or a
different type or proportion of lubricating oil, is likely to
call for some readjustment of the Needle-Valve.
Remember that, as a safety measure, it is advisable
to increase the Needle Valve opening by an extra
half-turn counter-clockwise, prior to establishing a
new setting. The same applies if the silencer type is
changed. A different silencer may alter the exhaust
pressure applied to the fuel feed and call for a revised
Needle-Valve setting.
The use of a different glowplug, or changes to the
mainrotor and its pitch angles may also require
compensating carburetor readjustments.
The correct functioning of the carburetor depends on
its small fuel orifices remaining clear. The minute
particles of foreign matter that are present in any fuel
can easily partially obstruct these orifices and upset
mixture strength so that engine performance
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,
occasionally remove the needle-valve holder from the
carburetor as shown in Photo and extract any
remaining foreign matter that may have lodged in the
location shown in right.
Remove this with
an 8mm spanner
Dirt and fbrous matter
mostly accumulate here
29
ADJUSTING CHART
Open the Needle Valve 1.5 turns from the fully closed position. Make sure that the Mixture Control Valve is at the factory setting.
A
Start the engine
Warm up the engine
B
C
Observe the mixture condition while "floating" the model
Turn the Mixture Control Valve counter-clockwise Idling OK
Turn the Mixture Control Valve clockwise
Lean mixture Rich mixture
DE
F
E
Observe the hovering mixture condition
Open the Needle Valve
(Turn counter-clockwise)
Hovering OK
Lean mixture Rich mixture
J
H
I
G
Close the Needle Valve (Turn clockwise)
Land the model
Idle for approx: 10 seconds, then reopen throttle to observe transition ("Float" the model)
Turn the Mixture Control Valve counter-clockwise Idle OK
Turn the Mixture Control Valve clockwise
Lean mixture Rich mixture
High Speed Flight
Open the Needle Valve (Turn counter-clockwise)
Lean mixture Rich mixture
L
M
Close the Needle Valve (Turn clockwise)
High Speed Flight OK
Fine tuning of hovering mixture
Turn the Needle Valve 2 or 3 clicks counter- clockwise, or turn the Mixture Control Valve 10-20 degrees counter- clockwise. Adjust pitch control characteristics.
Hovering OK
Response too sensitive
N
Response too slow
Adjustment completed
PQOQ
Turn the Needle Valve 2 or 3 clicks clockwise, or turn the Mixture Control Valve 10-20 degrees clockwise. Adjust pitch control characteristics.
K

30
CARE AND MAINTENANCE
Please pay attention to the matters
described below to ensure that your engine
serves you well in regard to performance,
reliability and long life.
As previously mentioned, it is vitally important
to avoid operating the engine in conditions
where dust, disturbed 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 Filters (L) and (S) are available
as optional extras.
Install an in-line fuel filter between the tank
and carburetor to prevent foreign matter in
the tank from entering the carburetor.
If these precautions are neglected, restriction
of fuel flow may cause the engine to cut out,
or the fuel/air mixture to become too lean
causing the engine to overheat.
Clean these filters periodically.
The use of modern high-performance alcohol
based model engine fuels, while promoting
cooler running, improved anti-detonation
combustion and increased power, have the
disadvantage of causing corrosion due to the
acid by-products of combustion.
The use of nitromethane in the fuel can also
contribute to the problem.
31
Do not close the needle-valve and mixture
control valve too far as this will cause a lean
setting and over heating of the engine. This
can, in turn, create nitromethane oxide
leading to internal rusting of the engine.
Always adjust the needlevalve slightly on the
rich side of peak rpm.
Do not leave unused fuel in the engine at the
conclusion of a day’s flying. Accepted
practice is to cut off the fuel supply while the
engine is still running at full throttle, then
expel as much fuel residue as possible by
turning the engine over 5-10 seconds with
the electric starter.
Finally, inject some after-run oil through the
glowplug hole and turn the engine over
several times by hand.
When the engine is not to be used for some
months (for example, as between flying
seasons), a worthwhile precaution is to
remove it from the airframe and, after
washing off the exterior with alcohol (not
gasoline nor kerosene), remove carefully the
carburetor with intake pipe, glow plug and all
silicone tubing and put them safely aside.
Then, immerse the engine in a container of
alcohol. Rotate the crankshaft while the
engine is immersed. If foreign matter is
visible in the alcohol, rinse the engine again
in clean alcohol. Finally, shake off and dry
the alcohol ,and inject some after-run oil in
the glowplug hole and rotate the crankshaft
several times by hand. Reinstall the
carburetor with intake pipe and glowplug on
the engine and keep it in a dry place after
putting in a vinyl bag.

32
TROUBLE SHOOTING
Symptom
Cause Corrective action
Engine fails to fire.
Fuel tank is empty.
Fuel not reaching the engine.
Fill the tank with fuel and repeat.
Priming procedure.
Glowplug element is burnt out.
Glowplug battery discharged
Replace glowplug.
Recharge or replace the battery.
Clogged fuel filter. Silencer inside is dirty. Clean or replace fuel filter. Clean inside silencer.
Over priming Remove glowplug and pump out excess fuel.
Fuel tubing is disconnected. Connect fuel tubing securely.
Fuel tubing is kinked, split or has a hole.
Check the tubing carefully and replace if necessary.
Incorrect carburetor settings Return the needle valve
and mixture control valve to basic position.
Incorrect servo linkage Reconnect linkage after setting servo at neutral.
Reverse rotating direction of electric starter. Mare sure the engine rotates counter clockwise
seen from crankshaft side.
33
Symptom
Cause Corrective action
Engine fires intermittently but does not run.
Insufficient fuel in the tank. Fill the tank with fuel.
Deteriorated glowplug Replace glowplug.
Clogged fuel filter
Silencer inside is dirty.
Clean or replace fuel filter.
Clean inside silencer.
Engine overheated Wait until engine has cooled.
Disconnecting plug battery too soon. Do not disconnect plug battery and wait until
the r.p.m. becomes stable.
Air bubbles in fuel Fit O rings to the tank screws to
prevent bubbles.

34
Symptom
Cause Corrective action
Symptom
Cause Corrective action
Unstable idle
Unsuitable glowplug Use suggested glowplug in the instructions.
Unsuitable fuel Do not use extremely high nitro or low oil fuel.
Silencer is disconnected or is loose Install silencer securely.
Not reaching expected peak r.p.m.
Insufficient warming up or running-in. Set the needle only after warming up.
Complete running-in.
Silencer or manifold is not securely connected
or disconnected. Check the connections and secure them.
Fuel tubing from tank to is split or broken. Replace the tubing.
35
Symptom
Cause Corrective action
Symptom
Cause Corrective action
Poor response
Deteriorated glowplug Replace glowplug.
Incorrect carburetor settings Readjust low r.p.m. range with metering
needle and mixture control valve.
Poor r.p.m. drop
Too much throttle opening at idle. Lower the throttle trim to adequate position
to lower idle r.p.m.
Incorrect carburetor fitting Fit carburetor securely.
Inaccurate linkage Recheck the throttle opening against
the pitch angle.
Needle-valve closed too far. Open needle-valve slightly

36
ENGINE EXPLODED VIEW
Type of screw C…Cap Screw M…Oval Fillister-Head Screw
F…Flat Head Screw N…Round Head Screw S…Set Screw
＊
1
C.M3x15
C.M2.6x7
2
3
4
5
6
7
8
910 11
12
13
14
15
16
17
N.+M3.5X5
0.2mm
37
The specifications are subject to alteration for improvement without notice.
ENGINE PARTS LIST
1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17

Heatsink Head Cylinder Liner Piston Ring Piston Piston Pin Piston Pin Retainer (2pcs.) Connecting Rod Carburetor Complete 20M Propeller Nut Thrust Washer Crankshaft Bearing (Front) Crankcase Crankshaft Bearing (Rear) Crankshaft Gasket Set Cover Plate Screw Set Throttle Lever Assembly Glow Plug No.8
No. Description
Code No.
23414300 23413100 25403400 23413200 23406000 24517000 23415000 23483000 23210007 22620003 22831000 23411000 23730000 23412000 23424000 23427000 23411300 27381410 71608001

38
CARBURETOR EXPLODED VIEW
C…Cap Screw M…Oval Fillister-Head Screw
F…Flat Head Screw N…Round Head Screw S…Set Screw
Type of screw
＊
N.+M3.5x5
12
3
5
8
C.M3x8
1-1
4
5-1
5-2
5-3
5-4 5-5
5-6
6
6-1
6-2
7
39
CARBURETOR PARTS LIST
The specifications are subject to alteration for improvement without notice.
Description
Code No.
No.
Throttle Lever Assembly
Throttle Lever Retaining Screw (2pcs.)
Carburetor Rotor
Carburetor Body
Rotor Guide Screw
Needle Valve Assembly
Needle Assembly
"O" Ring (2pcs.)
Needle Valve Holder Assembly
Needle Valve Holder
Ratchet Spring
Fuel Inlet (w/Gasket)
Mixture Control Valve Assembly
"O" Ring (L) (2pcs.)
"O" Ring (S) (2pcs.)
Carburetor Rubber Gasket
Carburetor Retaining Screw (2pcs.)
1
1-1
2
3
4
5
5-1
5-2
5-3
5-4
5-5
5-6
6
6-1
6-2
7
8
29085140
22826131
23483200
23483100
45581820
27081900
27981910
24981837
46181940
46181941
26711305
46181950
21285600
46066319
22781800
22615000
23081706