O.S. engine MAX-15 Setup guide

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.
●
●

CONTENTS
SAFETY INSTRUCTIONSAND WARNINGS
ABOUT YOUR O.S. ENGINE
INTRODUCTION
INSTALLATION OF THE ENGINE
INSTALLATION OF SILENCER
NEEDLE-VALVE LOCATION
BEFORE STARTING
PLUMBING AND
FUEL TANK POSITION
ADVICE ON SELECTION OF FUEL,
GLOW PLUG & PROPELLER
STARTING THE ENGINE
RUNNING-IN (Breaking-in)
TROUBLE SHOOTING WHEN THE
ENGINE FAILS TO START
CARE AND MAINTENANCE
ENGINE EXPLODED VIEW &
PARTS LIST
THREE VIEW DRAWING
OPTIONAL PARTS & ACCESSORIES
2 ~ 6
7
8
9
10
~ 12
12
14
~ 22
14
~ 20
21
~ 22
20
23
24
~ 27
30
28 ~ 29
9
~ 10
1

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.
2

WARNINGS
Model engine fuel is poisonous. Do not
allow it to come into contact with the eyes
or mouth.Always store it in a
clearlymarkedcontainerand
out of the reach of children.
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
anythingelsewhichmightignite
it.Donotsmokeorallowanyone
else to smoke, near to it.
•
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' 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.
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.
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.
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 fit 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
inanyway,unlessyouarehighlyexperienced
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"LA-SSeries"enginesaredesignedforcontrol line
models. They have broad power characteristics which
are suitable for both trainer models and stunt models.
Aseparate needle-valve is mounted at the rear, where
manual adjustment is safely away from the rotating
propeller.
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
Venturi
Silicone Tube
Crankshaft
Propeller nut
Propeller washer
Drive Hub Crankcase
Needle valve
Cover Plate
Fuel outlet
Fuel inlet
Glowplug
Connect the short length of fuel tubing supplied
securely between the fuel outlet and the fuel inlet. In
the event of the tube 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.
Length
15LA-S
25LA-S
40/46LA-S
51
~
52mm
55
~
56mm
65
~
66mm
7

INSTALLATION How to fasten the mounting screws.
Hardwood mounting beams
O.S. radial motor mount
(cast aluminum)
Tighten second nut firmly
down onto first nut.
Tighten this nut first.
Steel washer
3mm steel screw
Spring washer or
lock washer
Hardwood such as
cherry or maple.
Spring washer
3mm steel Allen screw
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. Opposite beam
Top surfaces
are not in the
same plane.
Engine does
not seat firmly.
Rigid hardwood
(e.g. maple)
Installation in the model
A typical method of beam
mounting is shown below,left. O.S. radial motor mount
(Available as an optional extra part.
See parts list)
Make sure that the mounting beams are parallel
and that their top surfaces are in the same plane.
At least
12mm(1/2")
At least
12mm(1/2")
3mm steel nuts
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.
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.
INSTALLATION OF SILENCER
Assembly screw Cone baffle
Turn to requlred position
Exhaust outlet
Locknut
Exhaust pressure nipple
Modelenginesgenerateconsiderableheat.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.
Reminder!
As delivered from the factory, the MAX-40LA & 46LA
have the needle-valve assembly installed vertically.
However, if more convenient for a particular
installation, the needle-valve may be reinstalled
horizontally.
The procedure for relocating the needle-valve is as
follows:
NEEDLE-VALVE LOCATION
9

Finally, secure the complete assembly to rear cover
plate as before.
3.
As self-tapping screws are used for unit
attachment, screw them in carefully so that screw
threads match those of the unit body precisely.
Note:
Remove the two cover-plate screws which secure
the needle-valve assembly bracket, then carefully
remove the two screws by which the needle-valve
unit is attached to the bracket.
Rotate the needle-valve unit through 90˚ and re-
attach it to the bracket in the required position.
Vertical position
Horizontal position
Cover plate fitting holes
Needle Valve unit
Needle Valve unit attachment screws
Needle-Valve
Assembly Bracket
1.
2.
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 8X4 (15LA-S), 9X6 (25LA-S),11X5
(40LA-S), or 11X6 (46LA-S).
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).
1.5 volt heavy-duty
dry battery or 2 volt rechargeable lead-acid cell (at least 5Ah)
If a 2-volt cell is employed,
use a resistance wire, as
shown, to reduce applied
voltage, otherwise the element
will overheat and burn out.
10

Resistance coil
(nichrome wire)
Adjust applied voltage by
changing the position of clip
on resistance coil until
glowplug element is glowing
bright red.
Battery leads
Raise
voltage to
increase
brightness.
Lower voltage to
reduce brightness.
Warning (Very hot)
5 Plug wrench
Used for tightening glowplug. The O.S. long plug
wrench is available as an optional accessory.
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 commercially available.
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, oneofthe
purpose-made manual or
electric fuel pumps may be used
to transfer fuel directly from your
fuel container to the fuel tank.
9 Fuel can filter
Fit a filter to the outlet tube of
your refuelling container to
prevent entry of foreign
matter into the fuel tank.
(R/C clunk tank installation)
For tightening
glowplug
Fuel bulb
Battery leads
Manual
Electric
Fuel pumps
Fuel Can Filter
12V Battery Starter
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.
Never touch
the nichrome
wire while
the battery is
connected.
7 Fuel tank
For installation in the model, a 40cc(1oz.) for 15LA-S,
a 60cc(2oz.) for 25LA-S, a 120cc(4oz.)-140cc(5oz.) for
40.46LA-S, is suggested.
11

Make sure that there are no kinks or folds in the
plumbing.
Silicone tubing
Use knife or
razor blade. Do not use wire
cutters or pliers
Note: When cutting silicone tubing......
*If you should need to clean out silicone tubes, use methanol or
glow-fuel, not gasoline.
Note:
Control line models tend to receive more abrupt changes of
attitude than R/C models,which results in air bubbles being
drawn from the fuel tank. Pay careful attention to the
plumbing and fuel tank position.
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 at left.
Fuel
Use a good quality commercial fuel or one of the blends
shown in the table. Fuel "A" is suitable for running-in and
ordinaryuse.Fuel"B"isforusewhenmorepowerisrequired
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.Useonlymaterialsofthehighestpurity.Synthetic
oilsare permissible but are less tolerant ofa "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 more powerful 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.
ADVICE ON SELECTION OF FUEL, GLOWPLUG & PROPELLER
5 ~ 8 mm
(example)
15LA-S
25LA-S
40/46LA-S
11.5mm
12mm
13mm
A
A
PLUMBING AND FUEL TANK POSITION
Measurement A (height from the
bottom surface of the mounting lug
to the center of the spray bar)
Metal control line fuel tank installation
R/C clunk tank installation
Make sure that the center of the spray
bar and tank are on the same line.
12

AB
75%
20%
5%
65%
20%
10%
Methanol
Castor Oil
Nitromethane
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.
Reminder!
8✕4
9✕6
11✕5
11✕6
15LA-S
25LA-S
40LA-S
46LA-S
8✕4
~
6
9✕6,10✕5
11✕5
~
6
11✕6
~
7,12✕5
~
6
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 will require in flight
experimentation.
Aerobatic & 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.
Running-in
Reminder!
GLOWPLUG
An O.S. A3 glowplug is installed in 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.
The role of the glowplug
With a glowplug engine, ignition is initiated by the
applicationofa1.5-voltpowersource.Whenthebattery
isdisconnected,theheatretainedwithinthecombustion
chamber remains sufficient to keep the plug filament
glowing,therebycontinuingtokeeptheenginerunning.
Ignition timing is 'automatic' : under reduced load,
allowing higher rpm, the plug becomes hotter and,
appropriately, fires the fuel/air charge earlier;
conversely,atreducedrpm,theplugbecomecoolerand
ignition is retarded.
13

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.
However, plug life can be extended and engine
performance maintained by careful use, i.e.:
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.
•
•
•
•
•
•
•
•
STARTING THE ENGINE Preparations
1Installing the glowplug
Installthewasherontheglowplugand
screw carefully into cylinder-head,
making sure that it is not cross-
threaded before tightening firmly. Glow plug
Washer
2Installing the propeller
First, mount 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.
Glowplug life
Particularly in the case of very high performance
engines,
glowplugs must be regarded as expendable
For accurately centering the
starter's rubber drive insert,
use an O.S. solid alloy
spinner-nut. (Available as an
optional extra part).
Alternatively, a spinner
assembly, enclosing the
propeller boss, may be
used, but make sure
that it is of sturdy construction and that the spinner
shell does not loosen when the starter is used.
Wrench
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 as indicated (i.e. with blades horizontal) when
turning the propeller in the direction of arrow.
3 Filling the fuel tank
Do not allow fuel to overflow into
silencer when refuelling, otherwise
engine may become flooded and
difficult to start.
Fuel pump
Use a fuel can filter
(e.g. O.S. Super Filter).
Re-connect
delivery tube
to engine after
tank is filled.
Disconnect delivery tube
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)
1
2
Close Open
Close
Open
Open the needle-valve 3 turns (for 15LA-S), 1 turns(for
25,40,46LA-S) in the direction of arrow from the closed
position.
4Opening and closing of the needle-valve
5Setting the needle-valve
Turn needle-valve clockwise to close (for leaner mixture).
Turn needle-valve counter-clockwise to open (for richer mixture).
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.
15

Fuel inlet
Fuel Tube
Fuel will flow
from tank to
venturi as
propeller is
turned.
Place your finger
over the venturi
to choke intake.
Turn the propeller
two revolutions
while watching
the fuel line.
6Priming 7Hold model securely when starting
Starter
Assistant
Assistant should hold
the model so that it
cannot move forward
when the engine starts.
Be careful not
to be hit by propeller!
Glowplug battery.
Place as far to the
rear as possible.
8Heat glowplug
Starting battery
Connect battery leads as shown
(polarity is immaterial.)
Turn the engine for 3
to 4 seconds by an
electric starter without
connecting glowplug
battery.
16

9Apply electric starter
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.
BEWARE of
the rotating
propeller.
10 Engine starts
If the engine does not start, refer to the TROUBLE
SHOOTING CHART .
In the interests of safety, keep your face and other parts of the
body away from the vicinity of the propeller.
Warning!
Since a control line engine is started with the
throttle fully opened and reaches full rpm right
after starting, be sure to hold the model securely.
17

Listen to the sound
carefully.
11 Needle-valve adjustment(1)
Then gradually close the needle-valve until the exhaust sound
changes from an irregular pitch (four-cycle) to a steady pitch
(two-cycle). Close the needlevalve
gradually until the engine
sound is changing from a
four-cycle into a two-
cycle in pitch.
12 Disconnect battery leads
Disconnect the battery leads
from the engine with care so
that the plug clip does not
touch the rotating pro-peller.
If the engine stops when battery leads are disconnected, close
the needle-valve a little (approx. 45˚) further, and restart the
engine.
13 Needle-valve adjustment(2)
As the needle-valve is closed beyond the initial readjustment,
the r.p.m. of the engine will be increased and a continuous
high-pitched exhaust note, only, will be heard.
Key to the needle-valve
adjustment.
(Turn 20-30˚ at a time.)
Turn the needle-valve 20-30˚ in the direction of arrow, and wait
momentarily for the change of r.p.m.
After the r.p.m. of the engine increases, turn the needle-valve
another 20-30˚ 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 per-
formance, 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 20.
18

14 Needle-valve adjustment(Summary)
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").
"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.
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.
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
20~30˚
Intermittent, high-pitched
two-stroke note superimposed
on low "four-stroke" sound.
NOTE: The above sketch is for reference purposes only.
Actual needle positions may differ from those shown.
On starting from cold, with the needle-valve
set at the rich starting position:
Take note of this position of the needle-valve.
This will produce the practical best (i.e. optimum)
rpm setting (lower than maximum rpm).
A light grey exhaust emission may be observed.
Now, re-open needle-valve 20-30˚
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.
Finally:
exhaust note is now a steady high-pitched sound,rising
higher in pitch as needle-valve is closed and increase.
The grey smoke will be lighter.
(However, make sure that engine is fully run in.)
Further needle-valve closure:
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 colour.
As the needle-valve is closed and the r.p.m. increases:
a good deal of white smoke is emitted, accompanied by
a relatively low-pitched "four-stroke" exhaust note.
77
1
2
5
4
3
19