O.S. Engines 95AX User Manual

It is of vital importance, before attempting to operate
your eng ine, to read the gene ral '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

8

9

10

20-21

22

27-30

33

15-17

SAFETY INSTRUCTIONS AND WARNINGS
ABOUT YOUR O.S. ENGINE

MAX-75AX 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

STARTING

CONTENTS

RUNNING -IN, IDLING ADJUSTMENT CHART

MIXTURE CONTROL VALVE ADJUSTMENT

REALIGNMENT OF MIXTURE CONTROL VALVE,
SUBSEQUENT STARTINGPROCEDURE

SUBSEQUENT READJUSTMENT,
CARBURETOR CLEANLINESS

TROUBLE SHOOTING WHEN THE
ENGINE FAILS TO START

CARE AND MAINTENANCE

ENGINE/

CARBURETOR

EXPLODED

VIEWS & PARTS LIST

O.S. GENUINE PARTS & ACCESSORIES

THREE VIEW DRAWING

MEMO

31

32

34-35

36-37

38-45

48-49

11-14

18-19

23

46-47

50

24-26

7

2

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.

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

Th e se co v er ev e nts wh ich
mig h t inv o lve se rious (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

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.

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.

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 al so 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.

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' recommenda­tions, using appropriate screws and lock­nuts.

Be sure to use the silencer (muffler)
sup plied wit h 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
uns afe. Never attempt to repair such a
propeller: destroy it. Do not modify a propeller
in any way, unless you are highly experienced
in tuning pr op ellers for spec ialized
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 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!

7

Piston

Cylinder Liner

Crankshaft

MAX-75AX

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 No.8
(suppplied with the engine)

Needle Valve Extension Cable Set

E-4040 Silencer Assembly

Silencer Retaining Screw (M4x40 2pcs.)

ABOUT THE ENGINE

E-4040 silencer (POWER BOX) develops
very effective muffling.
Also, the compact body enables it to be fit
within most cowls.

These are high performance two stroke
engines designed for sport and aerobatic
models.

Ample power enables to turn a one size
larger propeller with lower rpm, which
results in mild and pleasant exhaust sound.

The new carburetors needlevalve assembly
has now been angled backward for safety.

This manual handles

MAX-

75AX &

MAX-

95AX

RING

.

75AX/95AX

10

BASIC ENGINE PARTS

Cylinder head

Carburetor Type 61A

Crankshaft

Propeller nut

Propeller washer

Drive Hub

Crankcase

Cover Plate

Glowplug

Beam Mount

Lock nut

MAX-75AX is shown.

(Type 61C For 95AX)

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,

Propellers

13x8-10, 14x6-8

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 larger­diameter/lower-pitched prop is used.

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.

Spinner

SIZE(DxP)

14x8, 15x6-8, 16x6-8

75AX
95AX

Since the 75AX and 95AX 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.

12

FUEL

The 75AX and 95AX 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 18% 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 yo u ar e
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.

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!

Fuel Tank

A fuel tank of approximately
350cc capacity for 75AX and
450cc capacity for 95AX is suggested.
This allows around 10 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.

13

S

GLOWPLUG IGNITER

Commercialy available handy
glowplug heater in which the
glowplug battery and battery leads are integrated.

Alter natively, 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, 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, 3.0mm

Necessary for carburetor adjustments.

Phillips Screwdriver

No.2, etc.

LONG SOCKET WRENCH WITH PLUG GRIP

Recommen de d for easy removal and
replacement of the angled and recessed
glo wplug, the O.S.Long Socket Wrench
incorporates a special grip.

End Wrenches

8mm, 12mm, 14mm, etc.

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.