O.S. Engines 120AX 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.
CONTENTS
SAFETY INSTRUCTIONS AND WARNINGS
ABOUT YOUR O.S. ENGINE
NOTES WHEN APPLYING AN ELECTTRIC STARTER
ABOUT THE ENGINE
BEFORE STARTING
GLOWPLUG
BASIC ENGINE PARTS
INSTALLATION
INSTALLATION OF SILENCER & ADAPTERS
FUEL T ANK LOCA TION
NEEDLE-VALVE EXTENSION,
THROTTLE LINKAGE
PROPELLER & SPINNER ATTACHMENT
2-6
9-12
14
15-16
17-19
20-21
23-24
MIXTURE CONTROLS, STARTING
RUNNING -IN, IDLING ADJUSTMENT CHART
7
MIXTURE CONTROL VALVE ADJUSTMENT,
8
REALIGNMENT OF MIXTURE CONTROL VALVE
13
22
SUBSEQUENT STARTINGPROCEDURE,
SUBSEQUENT READJUSTMENT
CARBURETOR CLEANLINESS
TROUBLE SHOOTING WHEN THE
ENGINE FAILS TO START
CARE AND MAINTENANCE
ENGINE EXPLODED VIEWS & PARTS LIST
CARBURETOR EXPLODED VIEWS& PARTS LIST
GENUINE PARTS & ACCESSORIES
THREE VIEW DRAWING
25-28
29-32
33
34
35
36-37
38-39
40-41
42-43
44
45-46
1
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.
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.
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
Model engine fuel is also highly
flammable. Keep it away fr om 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.
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.
4
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.
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 glowplugignition 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
NOTES WHEN APPL YING
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 getting
into your eyes.
7
ABOUT THE ENGINE
Two versions are available, the one is
without silencer, extension adaptor and 90
degree adaptor and the other is with all of
them.
This is a high performance two stroke
engine designed for sport and scale models.
Crankcase and cylinder head are of aeroshape design which give advantage of light
weight, compact size.
The new 70D carburetor needlevalve
assembly has now been angled backward
for safety.
New E-5020 silencer (POWER BOX)
develops very effective muffling.
Also, the compact body enables it to be fit
with in most cowls.
Extension adaptor and 90 degree adaptor
offer various silencer installations.
STANDARD ACCESSOIES
Glow Plug No.8
(suppplied with the engine)
Needle Valve Extension Cable Set
E-5020 Silencer Extention
Adapter
Silencer Extention Adapter
Retaining Screw (M4x90 2pcs.)
E-5020 Silencer 90 Adapter
Silencer 90 Adapter Retaining
Screw (M4x20 2pcs.)
E-5020 Silencer Assembly
Silencer Retaining Screw (M4x45 2pcs.)
8
BEFORE STARTING
Tools, accessories, etc.The following items are
necessary for operating the engine.
Propellers
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 speed the propeller
noise will increase if blade tip is raised, due to
higher rpm or if a larger-diameter/lower-pitched
prop is used.
Sport
15x10-12, 16x8-10
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.
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.
Spinner
Since the 120AX
RING
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.
9
FUEL
The 120AX
RING
should be operated on a methanol
based fuel containing not less than 18% (volumetric)
castor oil, or a top quality synthetic lubricant (or a
mixture of both), plus a small percentage (5-20%) of
nitromethane for improved flexibility and power. (The
carburetor is adjusted a little on the rich side at the
factory for a fuel containing 20% lubricant and 15%
nitromethane.) Some commercial fuels also contain
coloring additives as an aid to fuel level visibility. In
some cases, these additives have indicated slightly
negative effects on the performance. We would
suggest that you use such fuels only if you are
satisfied that they do not adversely affect running
qualities when compared with familiar standard
fuels. When changing to a fuel brand or formula that
is different from the one to which you
are accustomed, it is a wise precaution
to temporarily revert to in-flight
running-in procedures, until you are
sure that the engine is running entirely
satisfactorily.
10
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 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.
Fuel Tank
A fuel tank of approximately
350cc capacity is suggested.
This allows around 10-12
minutes flying time, dependent
upon the type of fuel used, the size of propeller
and on the amount of full-throttle to part-throttle
operation throughout the flight.
GLOW PLUG
O.S. No.8 glowplug is supplied with the
engine.
GLOWPLUG IGNITER
Commercialy available handy
glowplug heater in which the
glowplug battery and battery
leads are integrated.
FUEL PUMP
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.
Electric Starter and
Starter Battery
Required when starting
the engine.
O.S. Super Filter (Fuel Can Filter)
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.
Manual
Electric
O.S. Non-Bubble Weight
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,
O.S. Non-Bubble Weight is available
as an optional extra.
Fuel Filter
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.
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.
11
TOOLS
HEX Screwdriver
Necessary for engine installation.
1.5mm, 2mm, 2.5mm, 3mm
Phillips Screwdriver
No.1, No.2, etc.
SCREWDRIVER
Necessary for carburetor adjustments.
No.1, No.2, etc
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.
8mm
End Wrenches
8mm, 12mm, 14mm, etc.
Socket Screwdriver
5.5mm, 7mm, 8mm
GLOWPLUG
Since the glowplug and fuel combination used
may have a marked effect on performance and
reliability, it would be worthwhile to experiment
with different plug types. A n O. S. No.8 glowplug is supplied with the engine.
Recommended O.S. plugs are the No.8 and A5.
Carefully install 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
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.
Needle Nose Pliers
12
Glowplug life
Particularly in the case of very high performance
engines,
glowplugs must be regarded as expendable
items.
However, plug life can be extended and engine
performance maintained by careful use, i.e.:
Install a plug suitable for the engine.
Use fuel containing a moderate percentage of
nitromethane unless more is essential for racing
events.
Do not run the engine too lean and do not leave the
battery connected while adjusting the needle.
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.
13
BASIC ENGINE PARTS
E-5020 Silencer Extention Adapter
E-5020 Silencer
Carburetor T ype 70D
Propeller washer
Propeller nut
Propeller Locknut
Crankshaft
Glowplug
Cylinder head
Cover Plate
Beam Mount
Crankcase
Drive Hub
14
INSTALLATION
Because the 120AX
use very substantial engine mounting. Conventional wooden mounting beams should be of rigid
hardwood and of at least 15mm or 5/8-in square section. Use at least 4mm steel screws, such as
Allen type, with locknuts, for bolting the engine to the bearers.
Front view
Top surfaces are in the same plane.
RING
is a powerful, large-displacement, single-cylinder engine, it is essential to
Make sure that the mounting beams are parallel and that their
top surfaces are in the same plane.
CORRECT
Side view
Top surfaces are not
in the same plane.
Re-align the surfaces
as necessary
INCORRECT
15
Opposite beam
Top surfaces are not in the
same plane.
Engine does not rest firmly.
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