O.S. engine MAX-75AX-BE User manual

It is of vital importance, before attempting to operate
your engine, to read the general 'SAFETY
INSTRUCTIONS AND WARNINGS' section on
pages 2-6 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.
1
2-6
7-8
9
10
20-21
22
28-31
15-17
SAFETY INSTRUCTIONS AND WARNINGS
ABOUT YOUR O.S. ENGINE
ENGINE CONSTRUCTION,
NOTES WHEN APPLYING AN ELECTTRIC STARTER
ABOUT THE ENGINE
BASIC ENGINE PARTS
BEFORE STARTING
INSTALLATION
INSTALLATION OF THE STANDARD ACCESSORIES
FUEL TANK LOCATION
MIXTURE CONTROLS
GLOWPLUG
CONTENTS
STARTING
RUNNING -IN, IDLING ADJUSTMENT CHART
MIXTURE CONTROL VALVE ADJUSTMENT
REALIGNMENT OF MIXTURE CONTROL VALVE,
SUBSEQUENT STARTINGPROCEDURE
TROUBLE SHOOTING WHEN THE
ENGINE FAILS TO START
CARE AND MAINTENANCE
ENGINE EXPLODED VIEW & PARTS LIST
CARBURETOR EXPLODED VIEW & PARTS LIST
O.S. GENUINE PARTS & ACCESSORIES
THREE VIEW DRAWING
32
33
34-35
36-37
38-39
40-41
11-14
18-19
23
42-43
44
24-27

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
WARNINGS
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.
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 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 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.
O.S. Bio - Ethanol fuel is not poisonous but
harmful. Do not allow it to be swallowed.
Always store it in a clearly marked
container and out of the reach of children.

4
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' recommenda-
tions, using appropriate screws and lock-
nuts.
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.
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.
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.
5
NOTES
Always check the tightness of the propeller
nut and retighten it, if necessary, before
restarting the engine. 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.
Preferably, use an electric starter. The
wearing of safety glasses is also strongly
recommended.
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 highly experienced
in tuning propellers for specialized
competition work such as pylon-racing.
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.

6
NOTES
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!
7
Piston
Cylinder Liner
Crankshaft
ENGINE CONSTRUCTION
Near TDC
Slight taper
When the engine is cold. When the engine is hot.
With this engine, the piston
will feel tight at the top of its
stroke (TDC) when the engine
is cold. This is normal.
The cylinder bore has a
slight taper. The piston and
cylinder are designed to
achieve a perfect running
clearance when they reach
operating temperature.

8
NOTES WHEN APPLYING
AN ELECTRIC 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
STANDARD ACCESSORIES
Glow Plug BE-3
(suppplied with the engine)
Needle Valve Extension Cable Set
E-4040 Silencer Assembly
Silencer Retaining Screw (M4x40 2pcs.)
ABOUT THE ENGINE
The MAX-75AX-BE has been developed and
designed to use O.S. Bio-Ethanol fuel only.
Therefore, some parts are different from
those of the MAX-75AX that use conventional
methanol based glow fuel. Also, special
attention is required in it’s handling.
This engine has been developed based on the
MAX-75AX, to use only O.S. Bio-Ethanol fuel.
It develops enough powerto fly general 61 size
sport models.
It is suggested to use propellers which develop
maximum r.p.m. of 8,500~9,500 so that you
may enjoy pleasant exhaust sound keeping it
low.
Glow plug, cylinder head, carburetor, drive hub
and silencer are different from those of the
MAX-75AX.

10
BASIC ENGINE PARTS
Cylinder head
Carburetor Type 61A-BE
Crankshaft
Propeller nut
Propeller washer
Drive Hub
Crankcase
Cover Plate
Glowplug
Beam Mount
Lock nut
11
Tools, accessories, etc. The following items
are necessary for operating the engine.
BEFORE STARTING
The choice of propeller depends on the design
and weight of the aircraft and 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 the propeller noise will
increase, due to higher rpm or if a larger-
diameter/lower-pitched prop is used.
Propellers
13x9-10, 14x6-8, 15x6
Sport
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.
Reminder!
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-controlled system.
DO NOT forget the WARNINGS and NOTES
on propeller and spinner safety given on
front pages.
Since the 75AX-BE is intended to
be started with an electric starter,
the addition of a spinner
assembly for centering the starter sleeve is
desirable. Use a heavy-duty, well balanced
spinner either of metal or plastic.
Spinner
It is suggested to use propellers which develop
maximum r.p.m. of 8,500~9,500 so that you
may enjoy pleasant exhaust sound keeping it
low.

12
FUEL
O.S. Bio-Ethanol fuel is not poisonous but
harmful. Do not allow it to be swallowed.
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.
Reminder!
A fuel tank of approximately
160~180cc capacity is suggested.
This allows around 10-12 minutes flying time,
dependent upon, the size of propeller and on
the amount of full-throttle to part-throttle
operation throughout the flight.
Fuel Tank
GLOW PLUG
Use the O.S. Bio-Ethanol fuel (BE-1).
Other fuel cannot be used with this engine.
Do not use conventional methanol based glow
fuel, or the engine will not run properly and
strong knocking may occur, which may cause
the propeller to fly off.
The engine is supplied with a special
glow plug (BE-3) designed for this
engine. Use 1.2V~1.5V the same as
conventional glow plugs.
This glow plug has a different thread
size for both the dia. and pitch
purposely so that conventional glow
plugs may not be installed.
13
1,2V〜1.5V
S
GLOWPLUG IGNITER
Commercialy available handy
glowplug heater in which the
glowplug battery and battery leads are integrated.
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.
FUEL PUMP
Manual Electric
Electric Starter and
Starter Battery
Required when starting
the engine. 12-Volt lead-acid battery
Electric
Starter
Install a filter on 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)
To prevent the pickup from adhering to
the tank wall under suction and
restricting fuel flow, slots may be filed I
the end of the weight. Alternatively, an
O.S. Non-Bubble Weight is available as
an optional extra.
It is recommended to install a good
in-line filter between the fuel tank
and carburetor to prevent entry of
foreign matter into the carburetor.
O.S. Non-Bubble Weight
Fuel Filter SILICONE FUEL LINE
Heatproof silicone tubing of
approx. 5mm o.d. and 2.5mm i.d.
is required for the connection
between the fuel tank and engine.

14
8mm
TOOLS
HEX Screwdriver
SCREWDRIVER
Necessary for engine installation.
1.5mm, 2.5mm
Necessary for carburetor adjustments.
Phillips Screwdriver
No.2, etc.
Socket Screwdriver
5mm, 5.5mm, 7mm
LONG SOCKET WRENCH WITH PLUG GRIP
Recommended for easy removal and
replacement of the angled and recessed
glowplug, the O.S.Long Socket Wrench
incorporates a special grip.
End Wrenches
12mm, 14mm etc.
Needle Nose Pliers
15
It is suggested to use as heavy and rigid as possible engine mounting for highest performance and
safe running. Conventional wooden mounting beams should be of rigid hardwood and of at least
15mm or 5/8-in square section. Use at least 3mm steel screws, such as Allen type, with locknuts, for
bolting the engine to the bearers..
INSTALLATION
CORRECT
Top surfaces are in the same plane.
INCORRECT
Front view Side view
Re-align the surfaces
as necessary
Opposite beam
Top surfaces are not in the
same plane.
Engine does not rest firmly.
Top surfaces are not
in the same plane.
Make sure that the mounting beams are parallel and that their
top surfaces are in the same plane.

16
How to fasten the mounting screws.
Hardwood mounting beams
Radial motor mount (cast aluminum)
Tighten second nut
firmlydown onto first nut.
Tighten this nut first.
Steel washer
3mm steel nuts
3mm steel screw
Spring washer or
lock washer
15mm min.
15mm min. Hardwood such as
cherry or maple.
Spring washer
3.5mm
steel Allen screw
● Make sure that these mounting beams are
accurately aligned and firmly integrated with
the airframe, reinforcing the adjacent
structure to absorb vibration. Use 4mm or
larger steel screws, preferably Allen type
hexagon socket head cap screws, with
washers and locknuts, for bolting the engine
to the bearers.
O.S. Radial Motor Mount
A special O.S. radial motor mount (Code
No.71905200) is available, as an optional
extra, for use where firewall type mounting is
required.
17
THROTTLE LINKAGE
Before connecting the throttle to its servo,
make sure that the throttle arm and linkage
safely clear any adjacent part of the airframe
structure, etc., as the throttle is opened and
closed. Connect the linkage so that the throttle
is fully closed when the transmitter throttle
stick and its trim lever are at their lowest
settings and fully open when the throttle stick
is in its fully-open position. Carefully align the
appropriate holes in the throttle arm and servo
horn so that they move symmetrically and
smoothly through their full travel.

18
INSTALLING THE GLOWPLUG
Install washer on glowplug
and insert carefully into
cylinder-head, making sure
that it is not cross-threaded
before tightening firmly.
Glow plug
Washer
NEEDLE-VALVE EXTENSION
The needle-valve supplied 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. For this purpose a Needle
Valve Extension Cable Set is supplied with the
engine. If a longer extension is reguired, cut a
commercially available rod to the required
length, bend one end to an L shape, insert it
into needle's center hole and secure it by
tightening the set-screw in the needle-valve
knob with 1.5mm Allen key.
Needle Valve
Extension Cable Set
1.5mm Allen key.
Set Screw
INSTALLATION OF THE STANDARD ACCESSORIES
19
INSTALLING SILENCER E40400 Silencer
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. Keep your hands and face away from
exhaust gas or you will suffer a burn.
Reminder!
The exhaust outlet of the silencer can be
rotated by 90 degrees the following manner:
Loosen the locknut and assembly screw.
Set the exhaust outlet at the required posi-
tion by rotating the rear part of the silencer.
Re-tighten the assembly screw, followed by
the locknut.
1)
2)
3)
Assembly screw
Locknut
Exhaust pressure nipple
Secure the silencer to the engine by means of
two retaining screws supplied after the engine
is securely mounted to a test bench or a
model.
It is recommended to seal the fitting faces of
engine exhaust and silencer with silicone
sealant.
Gasket
Baffle plate
Can be rotated
by 90 degrees.

20
Suggested fuel tank capacity is approx 160-
180cc. This will allow 10-12 minute flights.
Be sure to use a pressurized fuel system by
connecting the muffler pressure nipple to the
vent-pipe of the fuel tank.
FUEL TANK LOCATION
Make sure that the tank is well rinsed out
with methanol or glow fuel before installation
and that the pickup weight is well clear of the
bottom of the tank when held vertically.
Use a suitable length of best quality 5mm
OD x 2.5mm ID silicone tubing for fuel
tubing.
Fuel line weight should be 10mm away from
the tank bottom.
Locate the fuel tank so that the center line of
the tank is 10 to 15mm below the center line
of the needle-valve.
21
Attention to tank height
Plug (commercially available)
Approx. 15mm
Approx.
10-15mm
needle-valve Center Line
Fuel Tank
Center Line
Locate the fuel tank as close to the
engine as possible to minimize fuel
level pressure variation.
For Silencer
For carburetor
(to pressurize the fuel tank)

22
MIXTURE CONTROLS
The Needle Valve
When set to produce maximum power at full
throttle, this establishes the basic fuel/air
mixture strength. The correct mixture is then
maintained by the carburetor's built-in
automatic mixture control system to cover
the engine's requirements at reduced throttle
settings.
The Mixture Control Valve
This meters fuel flow at part-throttle and
idling speeds to ensure reliable operation as
the throttle is opened and closed. The
Mixture Control Valve is factory set for the
approximate best result. First run the engine as
received and readjust the Mixture Control Screw
only if necessary.
Two mixture controls are provided on this
Carburetor. Needle Valve
Mixture Control Valve
Mixture Control Valve of the carburetor is set at
basic position ( a little on the rich side) at the
factory. However, minor readjustment will be
required for atmospheric conditions and a
model. When a good result is not obtained with
the factory setting, readjust it according to the
MIXTURE CONTROL VALVE ADJUSTMENT
section. Please note during a running-in period
flights should be made with a slightly rich
needle setting. Therefore, during a running-in
period proper carburetor responses will not be
obtained. Adjust it at optimum position after the
running-in is completed.
23
GLOWPLUG
The role of the glowplug
Glowplug life
Be sure to disconnect the plug leads when
adjusting the needle-valve at higher r.p.m. range.
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.
An O.S. BE-3 glowplug is supplied with
the engine. Use only the O.S. BE-3 as
replacement. Carefully install plug finger-
tight, before final tightening with the
correct size plug wrench.

24
!

STARTING
Be sure to use an electric starter to
start the engine.
Fill the fuel tank with fuel. When filled,
prevent fuel 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).
25
Connect battery leads to glowplug.
Check that the needle-valve is closed. (Do
not overtighten.) Now open the needle-
valve counter-clockwise 4.5-5 turns to the
starting setting.
3.
4.
Open the throttle approx. one-quarter.
(This is to avoid unnecessarily
high r.p.m. when the engine starts.)
Turn needle-valve clockwise to close
(for leaner mixture)
Turn needle-valve counter-clockwise
to open (for richer mixture)
Mark
Close
Open
Fully closed
position
Fully opened position
Set at this point
1
4
3
4
5.
Set the throttle at 1/2 open and apply the
starter and press the starter switch for 5-6
seconds to prime the engine. 6.
Bring electric starter into contact with spin-
ner-nut or spinner and depress starter
switch for a short time. Repeat if necessary.
When the engine starts, withdraw the starter
immediately.
7.
Attention :
Do not choke the carburetor air intake when
applying the starter. This could cause an
excessive amount of fuel to be drawn into the
cylinder which may initiate a hydraulic lock and
damage the engine.

26
When the engine is started, open the throttle
slowly and adjust for the maximum r.p.m.
With this needle-valve setting, the mixture is
fairly rich. Close the needle-valve gradually
until just short of the peak r.p.m. Disconnect
the plug leads and further close the needle-
valve to the optimum position.
Then, close the throttle to idle, and open
smoothly to maximum r.p.m. If the r.p.m.
increases smoothly to maximum r.p.m., the
needle setting is OK.
If not, the needle setting is still rich. Close the
needle-valve further (10~15 degrees at a
time), and check the maximum r.p.m. If the
needle-valve is closed too much, the engine
will not accelerate and the r.p.m. decrease or
the engine will stop.
It is necessary to warm the engine up well so
that the fuel may vaporize sufficiently in order
for the engine to run steadily at maximum
r.p.m. When the temperature is lower (below
10 C), it will take some time for the engine to
be warmed up. Adjust the needle-valve until
the engine is sufficiently warmed up and r.p.m.
changes smoothly in proportion with the throt-
tle opening and closing.
The 75AX-BE requires some patience when
adjusting, so become acquainted with the
needle-valve setting procedure described
above.
Open the needle-valve 1/2~1 turn when
restarting the engine after the flight. Then, start
the engine and adjust the needle-valve after
warming the engine well up. (Longer warning
up time is required when the temperature is
low, while shorter warning up time is required
when the temperature is high.)
27
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.
How to stop the engine
Pull down the throttle lever and trim lever on
the transmitter fully.
Close
Note:
Until the engine warms up sufficiently, the
engine tends to stall or quit when the
throttle is opened before reaching the
maximum r.p.m. This is because the 75AX-
BE consumes much less fuel and the fuel is
not vaporized sufficiently.
Note:
Readjustments are required when a
propeller is changed even with a same size
of the same brand.
Once the optimum needle-valve is set, there
will be no need to change the setting in the
same day unless atmospheric conditions
change a lot. The optimum setting may vary
slightly according to the temperature and
atmospheric conditions.

28
Install the engine with the propeller intended
for your model. Open the needle-valve to the
advised starting setting and start the engine.
If the engine stops when the glow plug
battery is disconnected, open the needle-
valve to the point where the engine does not
stop.Run the engine for one minute with the
throttle fully open, but with the needle-valve
adjusted for rich, slow "four-cycle"operation.
RUNNING-IN (“Breaking-in”)
Now close the needle-valve until the engine
speeds up to "two-cycle"operation and allow
it to run for about 10 seconds, then reopen
the needle-valve to bring the engine back to
"four-cycle"operation and run it for another
10 seconds. Repeat this procedure until the
fuel tank is empty.
2.
All internal-combustion engines benefit from
extra care when they are run for the first few
timesknown as running-in or breaking-in.
This allows the working parts to mate together
under load at operating temperature.
Therefore, it is vitally important to complete the
break-in before allowing the engine to run
continuously at high speed and before
finalizing carburetor adjustments.
However, because O.S. engines are produced
with the aid of the finest modern precision
machinery and from the best and most suitable
materials, only a short and simple running-in
procedure is called for and can be carried out
with the engine installed in the model.
The process is as follows.
1.
29
Re-start and adjust the needle-valve so that
the engine just breaks into a "two-cycle" from
"four-cycle" operation, then make three or four
flights, avoiding successive "nose-up" flights.
3.
During subsequent flights, the needle-valve
can be gradually closed to give more power.
However, if the engine shows signs of
running too lean, the next flight should be
set richer. After a total of ten flights, the
engine should run continuously, at its
optimum needle-valve setting, without loss
of power as it warms up.
After the completion of the running-in adjust
the carburetor at optimum setting referring
to MIXTURE CONTROL VALVE
ADJUSTMENT section and SUBSEQUENT
READJUSTMENT section.
4.
5.
As the needle-valve is closed slowly and grad-
ually, the engine r.p.m. will increase and a
continuous high-pitched exhaust note, only,
will be heard. Close the needle-valve 10-15
degrees and wait for the change of r.p.m.
After the engine r.p.m. increases turn the nee-
dle-valve another 10-15 degrees and wait for
the next change of r.p.m. 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.
Optimum needle setting(1)
Optimum needle setting(2)
Slowly advance the throttle to its fully open
position, then gradually close the needle-valve
until the exhaust note begins to change. (4-
cycle to 2-cycle)

30
15-30
degrees
Needle-valve adjustment diagram
This diagram is for reference
purposes only.
Actual needle positions may
differ from those shown.
Note :
Practical best(optimum) needle-valve setting
Exhaust note starts to change.
Disconnect battery
leads from glowplug at
about this point.
Clear, high-pitched two-stroke
exhaust note Maximum rpm
setting("Lean").
STARTING
"Rich" needle-valve
setting when starting
the engine.
The engine may stop if the battery leads
are disconnected from the glowplug
while the engine is running rich.
E
n
g
i
n
e
s
t
o
p
s
R
e
v
o
l
u
t
i
o
n
s
s
t
a
r
t
t
t
o
d
e
c
r
e
a
s
e
.
t
o
d
e
Intermittent, high-pitched
two-stroke note superimposed
on low "four-stroke" sound.
Note: Although this is a two-stroke engine it fires like a four-stroke at these
rich needle-valve settings-i.e. ignition of the fuel charge takes place at
every fourth stroke of the piston instead of at every second stroke.
1
2
3
4
5
67
31
IDLING ADJUSTMENT CHART
Start the engine.
Make sure that the throttle is fully open.
Adjust the needle-valve.
Close the throttle gradually.
Set the idle speed
Open the throttle fully.
Does the engine regain full power?
Continue running at high speed for 10 seconds.
Close the throttle.
Run at idle speed for 5 seconds.
Does the engine stop?
Apply full throttle.
Does the engine
regain full power immediately?
OK
Refer to the next section.
Re-set the idle speed at a little higher r.p.m.
Adjust the idling.
Open the throttle smoothly.
15-30 open from maximum r.p.m. setting.
Yes.
No.
Yes.
Engine stops.
Engine stops.
Disconnect the plug leads just before the peak r.p.m.
Engine stops.

32
MIXTURE CONTROL VALVE ADJUSTMENT
With the engine running, close the throttle
and allow it to idle for about five seconds,
then open the throttle fully. If ,at this point,
the engine hesitates to pick up with thick
sound, the mixture is too rich. Correct this
condition by turning the Mixture Control
Screw clockwise 15-30 degrees.
If the mixture is excessively rich, the engine
may stop suddenly before picking up when
the throttle is fully opened, or with prolonged
idling the engine r.p.m. will drop gradually
and the engine stop.
If, on the other hand, the mixture is too lean,
the r.p.m. will not increase with a weak
sound or drop after increasing for a short
time and stop. In this case, turn the Mixture
Control Screw counter-clockwise 90 degrees
to positively enrich the idle mixture, then turn
Note: Mixture Control Valve adjustments
should be made in steps of 15~30
degrees initially, carefully checking
the effect, on throttle response, of
each small adjustment. Carrying out
adjustments patiently until the
engine responds quickly and
positively to the throttle control.
If the mixture is excessively lean, the r.p.m.
will increase gradually, then the engine stop.
the screw clockwise gradually until the
engine retains full power cleanly when the
throttle is reopened.
33
REALIGNMENT OF MIXTURE CONTROL VALVE
SUBSEQUENT STARTING PROCEDURE
Once the optimum needle-valve setting has
been established (see page 30, Needle-valve
adjustment diagram) the procedure for starting
may be simplified as follows.
Open the needle-valve 1/2~1 turn from the
optimum setting.
Set the throttle one-quarter open from the
fully closed position, energize the glowplug
and apply the electric starter. When the
engine starts, re-open the throttle and re-
adjust the needle-valve to the optimum
setting.
When re-starting the engine, take the same
procedure. Needle opening may vary to
temperature, humidity and season.
1.
2.
3.
Mixture Control Valve
Carburetor Body
Rotate the Mixture Control Valve until its
slotted head is flush with the carburetor
body, then screw it out one turn.This is the
standard position.
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. The basic position
can be found in the sketch shown below.
Screwed out
one turn.

34
1
2
3
Symptom Factor
Cause Corrective action
Recharge the electric starter battery.
Recharge lead-acid cell or replace dry battery. (Note: An unused, or almost
unused, dry battery may sometimes be of insufficient capacity if it is "old
stock".)
Replace glowplug. Check that applied voltage is not too high.
Check glowplug heating using other leads.
Close needle-valve fully and remove glowplug, then flip propeller to pump
out excess fuel. (Invert engine, if possible, while pumping out excess). Re-
start engine. (Priming is not necessary at this time.)
Repeat priming procedure referring to Priming.
Sluggish rotation
Glowplug battery
discharged.
Glowplug element is
burned out
Something wrong with
battery leads.
Engine "flooded" due to
excessive priming.
Insufficient priming.
Engine fails
to fire.
......
......
.....
....
....
.....
TROUBLE SHOOTING WHEN THE ENGINE FAILS TO START
Four key points
For quick, reliable starting, the following four conditions are required.
1 Good compression. 2 Adequate "glow" at glowplug. 3 Correct mixture.
4 Sufficient electric starter rotating speed.
If the engine fails to start, or does not keep running after being started, check symptoms against the
following chart and take necessary corrective action.
Note: The most common causes of trouble are marked with three asterisks, the less common problems
with one or two asterisks.
35
.....
........
......
......
.....
.......
.....
.......
...
Symptom Factor
Cause Corrective action
2
3
1
2
3
3
3
3
2
Voltage too high or too low. Re-check and readjust referring to "BEFORE
STARTING" .
Continue applying an electric starter. If the engine dos not start after more
than 4 tries, disconnect the current to the glowplug and leave for a few
minutes., then re-energize plug and apply starter. If the engine still does not
start, remove glowplug and pump out excess fuel by applying the starter.
Then re-start. (Priming is not necessary.)
Recharge the electric starter battery.
Recharge lead-acid cell or replace dry battery.
(Note: An unused, or almost unused, dry battery may sometimes be of
insufficient capacity if it is "old stock".)
Repeat priming procedure referring to Priming.
Close needle-valve half turn (180 ) and wait for several minutes then re-
start.(Priming is not necessary.)
Make sure that tank is filled with fuel. Check that there is not something
wrong with the fuel line (kinked or split). Check that carburettor is not
clogged with dirt.
Close the needle-valve a little before disconnecting current to the glowplug.
Change fuel or glowplug.
Incorrect heating of
glowplug.
Over priming.
Sluggish rotation.
Glowplug battery
discharged.
Insufficient priming.
Mixture too rich.
Fuel not reaching the
engine.
Mixture too rich.
Deterioration of glowplug
and/or fuel
Engine fires
intermittently but
does not run.
Engine fires once
or twice, then
fails to fire.
Engine starts but
rpm decreases
and engine eventually
stops.
Engine starts,
rpm increases
and engine cuts
out.
Engine stops when
the current to the
glowplug is discon-
nected after starting.

36
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.
Once opened, fuel deteriorates as days go
by. Use up as soon as possible after
opening the container. Also, keep it cool and
in a dark place.
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.
37
Do not close the needlevalve and mixture
control valve too far as this will cause a lean
setting and over heating 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.
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, 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 and glowplug on the
engine and keep it in a dry place after putting
in a vinyl bag.

38
ENGINE EXPLODED VIEW
C.M3x16
C.M3x8
2
1
3
4
5
6
7
8
9
10
12
11
13
14
15
16
Type of screw
C...Cap Screw
79871110 79871160
M3x8 M3x16
CAP SCREW SETS (10pcs./sets)
Code No. Size Pcs. used in an engine
Cylinder Head Retaining Screw (5pcs.)
Cover Plate Retaining Screw (4pcs.)
39
ENGINEN PARTS LIST
The specifications are subject to alteration for improvement without notice.

Description
Code No.
No.
1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16
27404010 27414010 27403000 27406000 27917000 27405000 27482020 45910100 27408010 29320000 27731000 27401000 29030001 27402000 27414020 27407000 71668100 72200080 27425000 29122540 27425300 22681957 26625210
Cylinder Head Head Gasket Cylinder & Piston Assembly Piston Pin Piston Pin Retainer (2pcs.) Connecting Rod Carburetor Complete (Type 61A-BE) Lock Nut Set Drive Hub Thrust Washer Crankshaft Ball Bearing (F) Crankcase Crankshaft Ball Bearing (R) Crankshaft Cover Gasket Cover Plate Glow Plug BE-3 Needle Valve Extension Cable Set E-4040 Silencer Assembly "O" Ring Assembly Screw Pressure Nipple (No.7) Silencer Retaining Screw (C.M4x40 2pcs.)