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.
SAFETY INSTRUCTIONS AND WARNINGS
ABOUT YOUR O.S. ENGINE
CONTENTS
TROUBLE SHOOTING WHEN THE
2~6
ENGINE FAILS TO START
26
~
27
INTRODUCTION
INSTALLATION OF THE ENGINE
INSTALLATION OF SILENCER
BEFORE STARTING
ADVICE ON SELECTION OF FUEL,
GLOW PLUG & PROPELLER
STAR TING THE ENGINE
RUNNING-IN (Breaking-in)
CARBURETTOR
15/25LA CARBURETTOR
AIR-BLEED ADJUSTMENT
10
12
14
23
7
8
9
~
12
~
14
~
22
23
~
24
25
CARE AND MAINTENANCE
OPTIONAL PARTS & ACCESSORIES
10LA ENGINE EXPLODED VIEW &
PARTS LIST
15/25LA ENGINE EXPLODED VIEW
& PARTS LIST
CARBURETTOR EXPLODED
VIEW & PARTS LIST
10LA THREE VIEW DRAWING
15/25LA THREE VIEW DRAWING
1
28
29
30
~
31
32~33
34
35
36
SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE
Remember that your engine is not a "toy", but a highly efficient internalcombustion 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.
The advice which follows is grouped under two headings according to the
degree of damage or danger which might arise through misuse or neglect.
WARNINGS
These cover events which
might involve serious (in
extreme circumstances, even
fatal) injury.
NOTES
These cover the many other
possibilities, generally less obvious
sources of danger, but which, under
certain circumstances, may also
cause damage or injury.
2
WARNINGS
Never touch, or allow any object to come
•
into contact with, the rotating
propeller and do not crouch
over the engine when it is
running.
A weakened or loose propeller may
•
disintegrate or be thrown off and, since
propeller tip speeds with powerful
engines may exceed 600 feet(180 metres)
per second, it will be understood that
such a failure could result in serious
injury, (see 'NOTES' section relating to
propeller safety).
Model engine fuel is poisonous. Do not
•
allow it to come into contact with the eyes
or 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.
•
Never operate your engine in an enclosed space. Model engines, like automobile engines, exhaust deadly carbonmonoxide. Run your engine only in an
open area.
Model engines generate considerable
•
heat. Do not touch any part of your
engine until it has cooled. Contact with
the muffler (silencer),
cylinder head or exhaust
header pipe, in particular,
may result in a serious burn.
3
NOTES
This engine was designed for model
•
aircraft. Do not attempt to use it for any
other purpose.
Mount the engine in your model securely,
•
following the manufacturers' recommendations, using appropriate screws and locknuts.
Be sure to use the silencer (muffler)
•
supplied with the engine. Frequent
exposure to an open exhaust may
eventually impair your hearing.
Such noise is also likely to cause
annoyance to others over a wide area.
If you remove the glowplug from the engine
•
and check its condition by connecting the
battery leads to it, do not hold the plug with
bare fingers.Use an appropriate tool or a
folded piece of cloth.
Fit 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.
4
NOTES
Always check the tightness of the propeller
•
nut and retighten it, if necessary, before
restarting the engine, particularly in the
case of four-stroke-cycle engines. If a
safety locknut assembly is provided with
your engine, always use it. This will prevent
the propeller from flying off in the event of a
"backfire", even if it loosens.
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 carburettor.
5
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!
6
INTRODUCTION
THE MAX-10LA,15LA,25LA have been developed to
meet the requirements of beginners and sport
flyers.
Of modern design and having a separate needlevalve unit mounted at the rear, where manual
adjustment is safely remote from the rotating
propeller, they offer the advantages of reliability
and easy handling, at lower cost. Like all O.S.
engines they are built to standards of engineering
excellence that have evolved through more than 60
years' experience in the design and production of
model internal-combustion engines. Advanced
modern precision machinery, top quality materials
and the efforts of highly skilled craftsmen and
technicians are combined to ensure a continuation
of the levels of performance, durability and
reliability for which O.S. is world famous.
The 'midnight blue' external finish may be
decolorized by very high surface temperature or
by certain solvents. Such decolorization does not
affect engine perfor-mance, however.
Cylinder head
Carburettor
Propeller nut
Crankshaft
Fuel inlet
Drive Hub
Propeller washer
Glowplug
Silicone Tubing
Crankcase
Fuel outlet
Needle valve
Cover Plate
Connect the short length of fuel tubing supplied
securely between the fuel outlet and the fuel inlet. In
the event of the tubing becoming damaged, it should
be replaced with a suitable length of best quality 5mm
ODX2mm ID silicone tubing. Use similar material to
connect the fuel inlet nipple to the fuel tank.
7
INSTALLATION
Installation in the model
A typical method of beam
mounting is shown below,left.
At least
12mm(1/2")
At least
12mm(1/2")
Make sure that the mounting beams are parallel
and that their top surfaces are in the same plane.
CORRECT
O.S. radial motor mount
(Available as an optional extra part.
See parts list)
Rigid hardwood
(e.g. maple)
INCORRECT
How to fasten the mounting screws.
Tighten second nut firmly
3mm steel nuts
Spring washer or
lock washer
down onto first nut.
Tighten this nut first.
12mm min.
Steel washer
12mm min.
3mm steel screw
Hardwood mounting beams
3mm steel Allen screw
Spring washer
Hardwood such as
cherry or maple.
Front view
Top surfaces are in the
same plane.
Side view
Top surfaces are not
in the same plane.
Re-align the surfaces
as necessary
Opposite beam
Top surfaces
are not in the
same plane.
Engine does
not rest firmly.
O.S. radial motor mount
(cast aluminum)
8
NEEDLE-VALVE EXTENSION
The needle-valve supplied with these engines 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.
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.
INSTALLATION OF SILENCER
The angled exhaust of the silencer can be rotated to
any desired position in the following manner:
1) Loosen the locknut and assembly screw.
2) Set the exhaust outlet at the required position by
rotating the rear part of the silencer.
3) Re-tighten the assembly screw, followed by the
locknut. The standard silencer is quite effective but
reduces power to some degree.
Exhaust pressure nipple
Reminder!
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.
9
Assembly screw
Cone baffle
Turn to requlred position
Exhaust outlet
Locknut
BEFORE STARTING
Tools, accessories, etc.
The following items are necessary for operating the
engine.
1 Fuel
Model glowplug engine fuel of good quality, preferably
containing a small percentage of nitromethane. (See
"Advice on selection of fuel, glowplug and propeller")
2 Glowplug
O.S. A3 glowplug is installed in the engine.
3 Propeller
Suggested size is 7x4(10LA), 8X4 (15LA), or 9X5
(25LA).
4 Glowplug battery
The power source for heating the glowplug may be
either a large heavy-duty 1.5volt dry cell, or preferably,
a 2-volt rechargeable lead-acid cell (accumulator).
If a 2-volt cell is employed,
use a resistance wire, as
shown, to reduce applied
voltage, otherwise element
1.5 volt heavy-duty
dry battery
or 2 volt rechargeable
lead-acid cell (at least 5Ah)
will overheat and burn out.
Warning (Very hot)
Never touch the nichrome wire while the battery is
connected.
Resistance coil
(nichrome wire)
Battery leads
Adjust applied voltage by changing the position of clip on
resistance coil until glowplug element is glowing bright red.
Raise
voltage to
increase
brightness.
Lower voltage to
reduce brightness.
5 Plug wrench
Used for tightening glowplug. The
O.S. long plug wrench is available
as an optional accessory.
For tightening
glowplug
10
6 Battery leads
These are used to conduct
current from the battery to the
glowplug. Basically, two leads,
with clips, are required, but, for
greater convenience, twin leads
with special glowplug connectors,
as shown on the right, are
Battery leads
commercially available.
7 Fuel tank
For installation in the model, a 70cc(2.5oz.) for 10LA,
a 100cc(3.5oz.) for 15LA, a 150cc(5oz.) for 25LA tank,
is suggested.
8 Fuel bottle or pump
For filling the fuel tank, a simple,
polyethylene "squeeze" bottle, with
a suitable spout,is all that is
required. Alternatively, one of the
purpose-made manual or electric
fuel pumps may be used to transfer
fuel directly from your fuel
Fuel bulb
Fuel pumps
container to the fuel tank.
9 Fuel can filter
Fit a filter to the outlet tube of
your refuelling container to
Fuel Can Filter
prevent entry of foreign
matter into the fuel tank.
(Refer to of STARTING
4
THE ENGINE section.)
10 Silicone tubing
This is required for the
connection between the fuel
tank and engine.
11 Electric starter and
starter battery
An electric starter is
recommended for starting.
12V Battery
Starter
Electric
Manual
11
Fuel and pressure lines
Connect suitable lengths of silicone tubing, as
illustrated, after installing the engine.
Plumbing and position of fuel tank
Locate the fuel tank so that the top of the tank is 510mm (1/4-3/8") above the level of the needle-valve.
Note: When cutting silicone tubing......
Use knife or razor blade.
*If you should need to clean out silicone tubes, use methanol
or glow-fuel, not gasoline.
Pay attention to tank height
Silicone tubing
Fuel level
6~8
mm
Do not use wire
cutters or pliers
Silencer (muffler) pressurized fuel system
To reduce variation in fuel "head" and ensure steady
fuel delivery at the carburettor, it is advisable to employ
a silencer (muffler) pressurized fuel system, i.e. to use
the silencer outlet nipple to pressurize the fuel tank as
shown left.
ADVICE ON SELECTION OF FUEL, GLOWPLUG & PROPELLER
Fuel
Use a good quality commercial fuel or one of the blends
shown in the table. Fuel "A" is suitable for running-in and
ordinary use. Fuel "B" is for use when more power is required
and for improved flexibility. Note that even a small quantity
of nitromethane (3-5%) will improve flexibility, making the
needle-valve adjustment less critical and improving throttle
response. Use only materials of the highest purity. Synthetic
oils are permissible but are less tolerant of a "lean run" than
castor-oil. If, therefore, a synthetic lubricant is used in the
fuel, readjust the needle-valve to a slightly richer setting, as
a safety measure, in case the fuel/air mixture becomes too
lean through maneuvers in flight. If a higher nitro fuel is used,
the engine should be checked out to make sure that it is
sufficiently run-in to operate on that particular fuel without
overheating. Do not use fuels containing less than 18%
lubricant.
12
A
Methanol
Castor Oil
Nitromethane
Reminder!
Model engine fuel is poisonous. Do not
allow it to come into contact with the eyes or
mouth. Always store it in a clearly marked
container and out of the reach of children.
Model engine fuel is also highly flammable.
Keep it away from naked 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.
PROPELLER
Suggested propeller sizes are given in the table. As
the ideal propeller diameter, pitch and blade area vary
according to the size, weight and type of model, final
propeller selection can be made after practical
experiment.
75%
20%
5%
B
65%
20%
15%
Reminder!
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.
LA Series
10LA
15LA
25LA
GLOWPLUG
An O.S. A3 glowplug is fitted to the engine.
Other recommended O.S. plugs are Nos.8 and A5.
Carefully fit plug finger-tight, before final tightening
with the correct size plug wrench.
Running-in
7✕4
✕
4
8
✕
5
9
Trainer & Sport
✕
3~5,8✕4
7
✕
5~6,8✕4~5
7
✕
5~6
9
The role of the glowplug
With a glowplug engine, ignition is initiated by the
application of a 1.5-volt power source. When the battery
is disconnected, the heat retained within the combustion
chamber remains sufficient to keep the plug filament
glowing, thereby continuing to keep the engine running.
Ignition timing is 'automatic' : under reduced load,
allowing higher rpm, the plug becomes hotter and,
appropriately, fires the fuel/air charge earlier;
conversely, at reduced rpm, the plug become cooler and
ignition is retarded.
13
Glowplug life
Particularly in the case of very high performance
engines,
glowplugs must be regarded as expendable
However, plug life can be extended and engine
performance maintained by careful use, i.e.:
Inatall a plug suitable for the engine.
•
Use fuel containing a moderate percentage of
•
nitromethane unless more is essential for racing
events.
Do not run the engine too lean and do not leave the
•
battery connected while adjusting the needle.
When to replace the glowplug
Apart from when actually burned out, a plug may
need to be replaced because it no longer delivers its
best performance, such as when:
Filament surface has roughened and turned white.
•
Filament coil has become distorted.
•
Foreign matter has adhered to filament or plug
•
body has corroded.
Engine tends to cut out when idling.
•
Starting qualities deteriorate.
•
STARTING THE ENGINE
Preparations
1 Installing the glowplug
Install washer on the glowplug
and insert carefully into cylinderhead, making sure that it is not
crossthreaded before tightening
firmly.
2 Installing the propeller
First, install the propeller on the engine by tightening
the prop nut or spinner-nut lightly, and make sure of
the position where compression is felt, turning the
propeller counter-clockwise slowly. Then tighten
firmly as explained below.
For accurately centering the
starter's rubber drive insert,
install an O.S. solid alloy
spinner-nut to the engine.
(Available as an optional extra
part).
Alternatively, a spinner
assembly, enclosing the
propeller boss, may be
used, but make sure
that it isof sturdy
construction and that the spinner shell does not
loosen when the starter is used.
Wrench
Glow plug
Washer
14
Warning: When using a spinner assembly, make
sure that the notches in the spinner shell are
large enough to clear the propeller blades and so
do not cut into and weaken the blade roots.
Tighten the spinner nut firmly so that compression is
first felt around this position (i.e. with blades
horizontal) when turning the propeller in the direction
of arrow.
3 Checking for gas leakage
Check gas leakage by
turning the propeller
up to this position after
compression is felt.
If leakage is detected, remove the
glowplug, carefully wipe threads,
re-insert and tighten firmly.
Dribble a few drops
of fuel around the
glowplug and look
for air bubbles.
Compression is first
felt around this posit
ion when turning
the propeller slowly.
4 Filling the fuel tank
Re-connect
fuel line
to engine after
tank is filled.
Fuel pump
Use a fuel can filter
(e.g. O.S. Super Filter).
15
Do not allow fuel to overflow into
silencer when refuelling, otherwise
engine may become flooded and
difficult to start.
Disconnect fuel line from
the fuel inlet, and connect
it to the tubing from the
fuel pump.
Do not let dirt or
dust enter fuel can.
Fuel (model
glow-plug
engine fuel)
5 Opening and closing of the needle-valve
Close
Open
Turn needle-valve clockwise to close (for leaner mixture).
Turn needle-valve counter-clockwise to open (for richer mixture).
6 Setting the needle-valve
Open the needle-valve 4 turns(for 10LA), 3 turns (for 15LA),
1
1 turns (for 25LA) in the direction of arrow from the closed
2
position.
Needle-valve
The position where the needle-valve stops is the fully closed
position. It may be convenient to remember the position of the
mark or set-screw at this time.
7 Open the throttle fully
Fully closed position
Fully opened position Throttle
8 Priming
Place your finger
over the carburettor
to choke intake.
Turn the propeller
two revolutions
while watching
fuel line.
16
Close
Open
Fuel Tube
Fuel inlet
Fuel will flow
from tank to
carburettor as
propeller is
turned.
Priming quantity
After fuel has been drawn to the carburettor, flip the
propeller two more revolutions, with intake choked, to
draw fuel into engine.
Above procedure is called priming.
NOTE (IMPORTANT)
The quantity of fuel drawn into the engine by
priming is an important factor in starting the
engine successfully.
When the engine is being started for the first time,
turn the propeller two revolutions after fuel reaches
the fuel inlet, as described above. However, when restarting the engine immediately after a run, one
revolution, or even no priming at all may be required.
The engine's requirements will be quickly learned
with experience.
9
Do not energize the glowplug at this stage.
Turn the propeller 3 to 4
turns counter-clockwise
smartly by finger in the
direction of arrow. Turn
approx. 10 turns instead
when the engine is cold.
17
10
Hold model securely when starting
Assistant should hold
the model so that it
cannot move forward
when the engine starts.
12
Heat glowplug
Glowplug battery.
Place as far to the
rear as possible.
Starter
Be careful not
to be hit by propeller!
11
Setting the throttle
Fully closed
position
1
3
Set at this Position.
2
3
Fully opened
position
Assistant
Connect battery leads as shown
(polarity is immaterial.)
13
Apply electric starter
18
Starting battery
Check that the throttle is one-third open from the fully
closed position. Bring the starter into contact with the
spinner nut or spinner and depress the starter switch
for one or two seconds. Repeat if necessary. When
the engine fires, withdraw the starter immediately.
Attention: Never place your finger over the
carburettor intake when applying the starter. Such an
action will cause an excess quantity of fuel to be
drawn into the cylinder and result in hydraulic lock
that may damage the engine.
14
Engine starts
If the engine does not start, refer to the TROUBLE
SHOOTING CHART on page 26-27.
BEWARE of
the rotating
propeller.
15
Needle-valve adjustment(1)
Slowly advance throttle to its fully open position, then gradually
close the needle-valve until the exhaust sound changes pitch.
Listen to the sound
carefully.
In the interests of safety, keep your face and other parts of the
body away from the vicinity of the propeller.
Close the needle-valve gradually until a high-pitched exhaust
note begins to be superimposed on the lower-pitched sound.
19
16
Disconnect battery leads
Disconnect the battery
leads from the engine
with care so that the
plug clip does not touch
the rotating propeller.
If the engine stops when battery leads are disconnected,
close the needle-valve a little (approx. 30˚) further, and restart
the engine.
17
Needle-valve adjustment(2)
As the needle-valve is closed beyond the initial readjustment,
the rpm of the engine will be increased and a continuous highpitched exhaust note, only, will be heard.
Key to the needle-valve
adjustment.
(Turn 10-15˚ at a time.)
Turn the needle-valve 10-15˚ in the direction of arrow, and
wait momentarily for the change of r.p.m.
After the rpm of the engine is increased, turn the needle-valve
another 10-15˚ 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.
IMPORTANT NOTE
When fine-tuning the needle-valve to reach peak performance, take care not to run the engine too lean
and cause it to overheat.
Be sure to observe the simple running-in procedures
described on Page 22.
20
18
Needle-valve adjustment(Summary)
67
Practical best(optimum) needle-valve setting
Clear, high-pitched two-stroke
exhaust note
Maximum rpm setting("Lean").
20~30˚
5
Intermittent, high-pitched
two-stroke note superimposed
on low "four-stroke" sound.
4
Disconnect battery leads from
glowplug at about this point.
3
Exhaust note starts to change.
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.
NOTE: The above sketch is for reference purposes only.
Actual needle positions may differ from those shown.
2
The engine may stop if the battery leads
are disconnected from the glowplug while
the engine is running rich.
e
R
o
t
E
e
n
n
i
g
s
s
t
p
o
1
"Rich" needle-valve
setting when starting
the engine.
t
t
e
r
d
a
t
s
o
t
s
.
n
e
s
o
i
t
a
u
e
l
r
o
c
v
e
d
On starting from cold, with the needle-valve
set at the rich starting position:
a good deal of white smoke is emitted, accompanied by
a relatively low-pitched "four-stroke" exhaust note.
As needle-valve is closed and rpm increases
an intermittent high-pitched two-stroke note will be superimposed
on the low-pitched "four-stroke" note.
Exhaust smoke will be less dense and grey in color.
Further needle-valve closure:
exhaust note is now a steady high-pitched sound,rising
higher in pitch as needle-valve is closed and rpm increases.
The grey smoke will be lighter.
(However, make sure that engine is fully run in.)
Finally:
maximum rpm is reached and will fall off (or engine will
stop) if needle -valve is closed any further.
Exhaust gas will be very light.
Now, re-open needle-valve 20-30˚
This will produce the practical best (i.e. optimum)
rpm setting (lower than maximum rpm).
A light grey exhaust emission may be observed.
Take note of this position of the needle-valve.
21
Subsequent starting procedure
Once the optimum needle-valve setting has been
established (see "Needle-valve adjustmentSummary") the procedure for starting is simplified as
follows:
1) Open the needle-valve one half-turn (180˚) from
the optimum setting.
2) Open the throttle fully, place your finger over the
carburettor intake and rotate the propeller through
two revolutions to prime the engine.
3) Set the throttle one-third open from the fully closed
position, energize the glowplug and apply the
starter. When the engine starts, re-open the
throttle and re-adjust the needle-valve to the
optimum setting.
Note: When re-starting the engine on the same
day, provided that atmospheric conditions have
not changed significantly, it may be practicable to
re-start the engine on its optimum (running)
setting. Also, if the engine is being re-started
immediately after a run (i.e.hot), priming should
not be necessary.
18
19
How to stop the engine
Close the throttle to reduce to the lowest possible r.p.m.
Close
With the transmitter throttle trim lever fully retarded, adjust the
throttle servo linkage so that the throttle rotor is fully closed
(i.e.engine stopped) when the stick is fully retarded.
22
RUNNING-IN ("Breaking-in")
All internal-combustion engines benefit, to some
degree, from extra care when they are run for the first
few times - known as running-in or breaking-in. This is
because the working parts of a new engine take a little
time to settle down after being subjected to high
temperatures and stresses. However, because O.S.
engines are made with the aid of the finest modern
precision machinery and from the best and most suitable
materials, only a very short and simple running-in
procedure is required and can be carried out with the
engine installed in the model.The process is as follows:
1) Start the engine and, with the throttle fully open,
open the needle-valve an extra half turn (180˚)
from the optimum setting. This will produce a rich
mixture that will result in cooler running. Allow the
engine to run out a full tank on the ground. (Avoid
dusty surroundings.)
2) Now fly the model with the needle-valve re-set 2030 degrees open from the optimum setting ( i.e.
40-60˚ from the highest rpm setting).
3) Close the needle-valve very slightly on successive
flights so that the engine is running on its optimum
needle setting at the fifth or sixth flight.
CARBURETTOR
These engines are equipped with a throttle type carburettor which provides a wide range of engine speed
control. With the throttle lever linked to a suitable
electric servo in the model, movement of the throttle
control on the transmitter will enable engine rpm to be
varied, proportionally, from idling speed to full power.
The carburettor of your engine has been factory set
for the approximate best results and no adjustment
(except to the needle-valve) should be required
provided that the fuel tank is correctly located, as
previously described. After the engine has been runin, check the operation of the throttle according to the
following chart. Re-adjust the controls only when
necessary.
23
Re-set the idling position at
a little higher r.p.m.
Start the engine.
Make sure that the throttle is
fully open.
Adjust the neede-valve.
Close the throttle gradually.
Find the idling position.
Fix the idling position.
Open the throttle fully.
20-30
˚
open from maximum
r.p.m. setting.
The position where the lowest
possible r.p.m. ,with steady
running, is obtained.
Set the throttle opening by
means of the throttle trim on
the transmitter so that the lowest
practical speed, without risk of
the engine stopping,is obtained.
24
Refer to the CARBURETTOR
AIR-BLEED ADJUSTMENT
section on page 25.
Engine stops.
Engine stops.
Engine stops.
Does the engine
regain full power?
Continue running at high speed
for 10 seconds.
Close the throttle.
Run at idling speed for 5 seconds.
Does the engine stop?
Apply full throttle.
Does the engine
regain full power
immediately?
OK
Yes.
No.
Yes.
CARBURETTOR AIR-BLEED ADJUSTMENT
Pre-Flight Check
Start engine and adjust needlevalve as previously described.
Close the throttle gradually.
Find the idling position.
approx.
Repeat the procedure while opening and closing
the throttle until the best result is obtained.
Hold the model.
Hold model level, then slowly raise its nose.
If revolutions increase.
15˚
If engine runs unevenly or stops.
25
Stop the engine.
Note: Stop engine by
pinching fuel delivery
tube. Do not touch
needle-valve.
These adjustments can be
made without stopping
the engine.
However, it is advisable for
beginners to stop the engine
for safety reasons.
Open air-bleed
screw.
Half turn at a
time.
Immediately point
nose down, so that
engine runs steadily
again.
Stop the engine.
Attention: Do not leave the glowplug connected to the battery
while adjusting the carburettor throttle.
approx.
15˚
Close air-bleed
screw.
Half turn at a
time.
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.
Symptom
Engine fails
to fire.
Factor
1
2
3
Cause
★
Sluggish rotation
Glowplug battery
★★
discharged.
Glowplug element is
★
burned out
Something wrong with
★
battery leads.
Engine "flooded" due to
★★
excessive priming.
★
Insufficient priming.
......
......
.....
....
....
.....
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 8 Priming.
26
Symptom
Engine fires
intermittently but
does not run.
Engine fires once
or twice, then
fails to fire.
Engine starts but
revolutions decrease
and engine eventually
stops.
Engine starts,
then revolutions
increase and
engine cuts out.
Engine stops when
battery leads are
disconnected after
starting.
Factor
2
3
1
2
3
3
3
3
2
Cause
Incorrect heating of
★★
glowplug.
Over priming.
★★
Sluggish rotation.
★
Glowplug battery
★★
discharged.
Insufficient priming.
★★
★★★
Mixture too rich.
Fuel not reaching the
★
engine.
Mixture too rich.
★★
Mismatch of glow plug and
★
fuel.
.....
........
......
......
.....
.......
.....
.......
....
Corrective action
Voltage too high or too low. Re-check and readjust referring to "BEFORE
STARTING" paragraph 4.
Continue flipping propeller. If engine does not start after more than 10 flips,
disconnect battery from glowplug and leave for a few minutes, then reenergize plug and flip prop again. If engine still does not start, remove
glowplug and pump out excess fuel by flipping prop quickly.
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 8 Priming.
Close needle-valve half turn (180˚) and wait for several minutes then restart.(Priming is not necessary.)
Make sure that tank is filled with fuel. Check that there is not something
wrong with fuel tubing (kinked or split). Check that carburettor is not
clogged with dirt.
Close the needle-valve a little.
Change fuel or glowplug.
27
CARE AND MAINTENANCE
To ensure that you obtain long life and peak performance
from your engine, observe the following.
Avoid running the engine under dusty conditions.
1.
If necessary, lay a sheet of plywood or hard-board
in front and under the nose of the model when
starting the engine.
Foreign matter in the fuel can cause the
2.
carburettor jet to be partially clogged.
Therefore:
rinse out the fuel tank with methanol or fuel before
•
installing it.
Install a fuel filter in the fuel line between tank and
•
carburettor.
Install a fuel filter in the outlet of your squeeze
•
bottle, or in the pump inlet if you use a manual or
electric pump.
do not leave your fuel container open needlessly.
•
check filters periodically and clean them when
•
necessary.
28
3.
Do not leave raw fuel in the engine at the
conclusion of a flying session: it may cause
corrosion. The best practice is to disconnect the
fuel line from the carburettor while the engine is
running. Remaining fuel in the tank should also be
drained off.
Clean the exterior of the engine with a clean cotton
4.
cloth.If this is not done, oil and dirt will burn onto
the outside of the engine each time it is run and
the engine will soon become blackened.
If the engine is not in use for a while (more than
5.
two months) remove the glowplug and rinse out
the interior with kerosene (not gasoline), by
rotating the crankshaft. Shake out residue, then
inject light machine-oil through the plug hole and
carburettor intake, again rotating the shaft to
distribute the protective oil to all working parts.
Gasoline, thinner, kerosene and light machine oil
cause swelling and deterioration of plastic parts,
"O" rings and fuel tubing. Use methanol for
cleaning these engines.
Avoid unnecessary dismantling of your engine.
6.
O.S. GENUINE PARTS & ACCESSORIES
RADIAL MOTOR MOUNT
■
(71909110) for 10LA
(71909310) for 15LA
(71908100) for 25LA
SILENCER EXTENSION
■
ADAPTORS
(21125108) for 10/15LA
(22325100) for 25LA
EXHAUST
■
ADAPTORS
(21125502) for 10/15LA
GLOW PLUG
■
A3
(71605300)
No.8
(71608001)
NEEDLE VALVE
■
EXTENSION CABLE SET
(72200080)
SPINNER NUT
■
M5 (20824005) for 10/15LA
1
(23024008) for 25LA
/
"-28
4
LONG PROPELLER NUT SET
■
(73101000) for 25LA
NON-BUBBLE WEIGHT
■
(71531000)
29
SUPER FILTER (L
■
(72403050)
LONG SOCKET WRENCH
■
WITH PLUG GRIP
(71521000)
)
EXPLODED VIEW
M.+M2.6X10
1
(MAX-10LA)
=
2
30
3
3
-1
8
7
6
5
4
Type of screw C…Cap Screw M…Oval Fillister-Head Screw
✽
F…Flat Head Screw N…Round Head Screw S…Set Screw
q
9
M.+M2.6X7
S.3X3
-
-1
0
-
-2
-
ENGINE PARTS LIST
(MAX-10LA)
Code No.
No.
2 1004 000
1
2 1003 000
2
2 1081 000
3
2 7881 120
3
-1
2 0810 007
4
2 1109 005
5
2 1758 000
6
2 1620 006
7
2 1001 000
8
31
2 1002 000
9
2 1007 000
0
2 1781 970
-
2 4981 837
-
-1
2 6381 501
-
-2
2 1014 000
=
2 1013 000
q
7 1605 300
2 1225 000
2 2681 957
2 2325 300
2 1125 409
Specifications are subject to alteration for improvement without notice.
Cylinder Head
Cylinder Piston & Connecting Rod Assembly
Carburettor Complete 10H
Carburettor Retaining Screw
Propeller Nut
Propeller Washer
Drive Hub
Thrust Washer
Crankcase
Crankshaft
Cover Plate
Needle
"O" Ring
Set Screw
Head Gasket
Screw Set
Glow Plug A3
871 Silencer
Pressure Fitting
Assembly Screw
Retaining Screw(N.+M2.6X25 2pcs.)
Description
EXPLODED VIEW
M.+M2.6X10(15LA)
N.+M3X12(25LA)
1
(MAX-15LA,25LA)
q
32
5
7
6
Type of screw C…Cap Screw M…Oval Fillister-Head Screw
✽
F…Flat Head Screw N…Round Head Screw S…Set Screw
3
5
-1
5
-2
0
9
8
2
4
N.+M3.5X5
w
-
B.+M2.6X8
S.3X3
=
=
=
=
-2
-1
=
-5
-4
=
-3
ENGINE PARTS LIST
Code No.
15LA 25LA
33
5
5
=
=
=
=
=
1
2
3
4
5
-1
-2
6
7
8
9
0
-
=
-1
-2
-3
-4
-5
q
w
21754000
21753000
21706000
21205040
21783000
21015001
20810007
21109005
21758000
21620006
21751000
21752000
21757000
21757100
21781970
21714100
21713000
21225000
22681957
22325300
21125409
22554000
22553000
22606009
22405013
22581000
22615000
23081706
23210007
24009000
22558000
22020001
22551000
22302000
22557000
22557100
26711305
24081970
24981837
26381501
22564000
22563000
71605300
22325020
22625404
(MAX-15LA,25LA)
Description
Cylinder Head
Cylinder & Piston Assembly
Piston Pin
Connecting Rod
Carburettor Complete
Carburettor Complete
Carburettor Rubber Gasket
Carburettor Retaining Screw(2pcs.)
Propeller Nut
Propeller Washer
Drive Hub
Thrust Washer
Crankcase
Crankshaft
Cover Plate Assembly
Cover Plate
Ratchet Spring
Needle
"O" Ring
Set Screw
Head Gasket
Screw Set
Glow Plug A3
871 Silencer
Pressure Fitting
Assembly Screw
Retaining Screw(N.+M2.6X25 2pcs.)
E-2030 Silencer
Retaining Screw(N.+M3X27 2pcs.)
(10G)
(20H)
Specifications are subject to alteration for improvement without notice.
CARBURETTOR EXPLODED VIEW & PARTS LIST
TYPE 10H
1
1
-1
2
N.+M2.6X6
N.+M3X4
5
✽
Type of screw
C…Cap Screw M…Oval Fillister-Head Screw
F…Flat Head Screw N…Round Head Screw S…Set Screw
1
1
2
3
4
5
2 1081 400
-1
2 4081 300
2 1081 200
2 1081 100
2 1081 300
2 7881 120
Code No.
Description
Throttle Lever Assembly
Throttle Lever Fixing Screw
Carburettor Rotor
Carburettor Body
Throttle Stop Screw
Carburettor Retaining Screw
4
3
TYPE 10G,20H
N.+M3X6
- 1
1
1
Code No.
10G
1
22081408
-1
1
22081313
21781200
2
21783600
3
21783100
4
21783300
5
21015001
6
7
Specifications are subject to alteration for improvement without notice.
23081706
34
N.+M2X14(10G)
N.+M2.6X15
2
3
N.+M3.5X5
20H
22381200
24081600
22581100
22581300
22615000
5
4
N.+M2X6(10G)
M.+M2.6X7
4
6
7
Description
Throttle Lever Assembly
Throttle Lever Fixing Screw
Carburettor Rotor
Air-bleed Screw
Carburettor Body
Throttle Stop Screw
Carburettor Gasket
Carburettor Retaining Screw
MAX-10LA THREE VIEW DRAWING
10LA SPECIFICATIONS
Displacement
■
Bore
■
Stroke
■
Practical R.P.M.
■
Power output
■
Weight
■
1.76 cc (0.107 cu.in.
13.44mm (0.529 in.
12.4mm (0.488 in.
~
2,500
0.27 bhp / 17,000 r.p.m.
112g (3.95 oz.
)
)
)
18,000 r.p.m.
)
M5x0.8
23
38.6
35
4-ø3.3
31.4
11
33.2
38.7 19.2
27.5
2-ø2.8
44.3
23.5
11.7
15.9
20
23.2
62
Dimensions(mm)
MAX-15LA/25LA THREE VIEW DRAWING
15LA SPECIFICATIONS
Displacement
■
Bore
■
Stroke
■
Practical R.P.M.
■
Power output
■
Weight
■
2.49 cc (0.1517 cu.in.
15.2mm (0.598 in.
13.7mm (0.539 in.
~
2,500
0.41 bhp / 17,000 r.p.m.
138g (4.87 oz.
25LA SPECIFICATIONS
Displacement
■
Bore
■
Stroke
■
Practical R.P.M.
■
Power output
■
Weight
■
4.07 cc (0.249 cu.in.
18.0mm (0.709 in.
16.0mm (0.630 in.
~
2,500
0.6 bhp / 15,000 r.p.m.
197g (6.94 oz.
18,000 r.p.m.
16,000 r.p.m.
)
)
)
)
)
)
)
)
UNF1/4-28 (M5)
Dimensions(mm)
39 (30.8)
46.5 (39.5)
36 (33)
14 (14.4)
32 (27.5)
60 (48.5)
74.5 (61)
30.5 (25.8)
29 (24.8)
44 (40)
36
22 (20)
67.5 (56.5)
( )15LA
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Copyright 2000 by O.S.Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan.
E
C
N
E
L
L
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C
X
E
F
O
S
D
6-15 3-Chome Imagawa Higashisumiyoshi-ku
Osaka 546-0003, Japan
TEL. (06) 6702-0225
FAX. (06) 6704-2722
110101
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