O.S. engine MAX-91FX 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.
●
●

SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE
FEATURES OF FX SERIES ENGINES, BEFORE
INSTALLING THE ENGINE
BASIC ENGINE PARTS
NEEDLE-VALVE LOCATION
INSTALLATION OF THE ENGINE
THROTTLE LINKAGE, SILENCER
FUEL TANK LOCATION
GLOWPLUG
FUEL, PROPELLERS
MIXTURE CONTROLS
BEFORE STARTING
RUNNING-IN (Breaking-in)
IDLING ADJUSTMENT CHART
MIXTURE CONTROL VALVE ADJUSTMENT,
REALIGNMENT OF MIXTURE CONTROL VALVE
SUBSEQUENT STARTING PROCEDURE
SUBSEQUENT READJUSTMENT
CARBURETOR CLEANLINESS,
ENGINE CARE AND MAINTENANCE
ENGINE EXPLODED VIEWS &
ENGINE PARTS LISTS
CARBURETOR EXPLODED VIEWS
& PARTS LISTS
GENUINE O.S. PARTS &ACCESSORIES
ENGINE THREE VIEW DRAWINGS
MEMO
STARTING
CONTENTS
17 ~ 18
2
~ 6
7
8
8
~ 9
10
11
~ 12
12
13
14
~ 15
15
16
~ 17
19
~ 21
22
23
24
25
36
~ 37
26
~ 33
34
~ 35
38
~ 41
42
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.
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.
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 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 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

This range of engines is ideally suited to a variety
of R/C aircraft, including trainer, sports, aerobatic
and scale types.
A separate precision-made needle-valve unit is
installed at the rear, where manual adjustment is
safely remote from the rotating propeller.
With the 50SX, 61FX and 91FX, the needle-valve
assembly can be installed either horizontally or
vertically.
FEATURES OF FX SERIES ENGINES
With these engines, the piston will feel tight at the
top of its stroke when the engine is cold. This is
normal. The piston and cylinder are designed to
achieve a perfect running clearance when they
reach their intended running temperature.
Note :
•
•
•
Carefully insert plug, with
washer, fingertight only, before
final tightening with the correct
size plug wrench.
BEFORE INSTALLING THE ENGINE
Installing the glowplug
Connect the short length of fuel tubing (supplied)
securely between the needle-valve outlet and
carburetor inlet as shown in the illustration on the
next page.
In the event of the tubing becoming damaged, it
should be replaced with a suitable length (as
indicated below) of best quality 5mm ODx2mm ID
silicone tubing. Use similar material to connect the
fuel inlet nipple to the fuel tank.
Connecting fuel tubing
Length
40¡46FX 54
~ 56mm 61FX
91FX
54 ~ 56mm
62mm
Glow plug
Washer
50SX
44
~ 46mm
Length
Glow Plug No.8, Silicone Tube, Instruction Manual
Common to accessories
50SX, 40/46FX
61FX
91FX
873 Silencer Assembly
E-4010 Silencer Assembly
E-4020 Silencer Assembly
Needle Valve Extension Cable
Type of engines Type of engines
7

The proce dure for relocating the needle-valve vertically
is as follows:
As delivered from the factory, the MAX-61FX and
MAX-91FXRING have their needle-valve assembly
installed horizontally. However, if more convenient for
a particular installation, the needle-valve may be
reinstated vertically behind the cylinder. (See sketch
opposite.) Please note that the needle-valve knob
has a center hole and set-screw for the fitting of a
piano-wire extension (supplied with the 91FX) so that,
when relocated vertically, the extension enables
adjustments to be made without risk of burning one's
fingers on the cylinder head.
NEEDLE-VALVE LOCATION
BASIC ENGINE PARTS
Cylinder head
Carburetor
Silicone Tube
Crankshaft Propeller nut
Propeller washer
Drive Hub Crankcase
Needle valve
Cover Plate
Fuel outlet
Fuel inlet
Glowplug
Fuel inlet
Beam Mount
MAX-61FX
Throttle
Lever
Throttle Stop Screw
Using 8mm wrench, remove complete needle-valve
holder assembly including needle, from side of
cover plate.
Remove fuel inlet assembly from upper boss of
cover plate.
Transfer banjo type fuel inlet including washers, to
needle-valve holder and carefully screw complete
assembly into upper boss vacated by fuel inlet
assembly. Tighten very carefully.
1.
2.
3.
8

Inlet Holder
Plug Screw (50SX/91FX)
Fuel Inlet
Needle-Valve
Assembly
Needle Extension
Inlet Holder
Fuel Inlet
Needle-Valve
Assembly
45mm
Fuel Inlet
Needle-Valve
Assembly Plug Screw (50SX/91FX)
Fuel Inlet
Needle-Valve
Assembly
Needle Extension
45mm
61FX
50SX/91FX
Use hexagon-head brass inlet holder (61FX) or
plug screw (50SX/91FX) to blank off side boss
vacated by needle- valve assembly.
4.
9

Hardwood mounting beams O.S. radial motor
mount
(cast aluminum)
How to fasten the mounting screws.
Make sure that the mounting beams are parallel and
that their top surfaces are in the same plane.
Front view Side view Top surfaces
are not in the
same plane. Opposite
beam Top surfaces
are not in the
same plane.
Re-align the surfaces
as necessary Engine does not
rest firmly.
CORRECT INCORRECT
Top surfaces are in
the same plane.
Tighten second
nut firmly down
onto first nut.
Tighten this
nut first.
Steel washer
3-4mm
steel screw
Spring
washer or
lock washer
Hardwood such
as cherry or maple.
Spring
washer
3.5mm steel
Allen screw
3-4mm steel nuts
Use mounting screws of a diameter
(between 3mm and 4mm) appropriate
to engine size (see table left).
Mounting Screw Size
50SX, 40¡46FX
61¡91FX
3mm
4mm
INSTALLATION OF THE ENGINE
Rigid hardwood
(e.g. maple)
At least
15mm(5/8")
At least
15mm(5/8")
O.S. radial motor mount
(Available as an optional extra
part. See parts list)
A typical method of beam
mounting is shown below, left.
Installation in the model
50SX
40¡46FX
61¡91FX
For 50SX, 40/46FX(Code No. 71913100)
For 60FP, 61¡91FX(Code No. 71905200)
10

The exhaust outlet of the silencer can be rotated to
any desired position in the following manner:
Loosen the locknut and assembly screw.
Set the exhaust outlet at the required position by
rotating the rear part of the silencer.
Re-tighten the assembly screw, followed by the
locknut.
SILENCER
1)
2)
3)
NOTE :
The standard expansion-chamber type silencer is
quite effective, but reduces power to some degree.
Assembly screw Cone baffle
Turn to requlred position
Exhaust outlet
Locknut
Exhaust pressure nipple
Before connecting the throttle-lever/servo linkage,
make sure that no part of the linkage interferes with
the internal structure of the aircraft or wiring, etc.,
when the throttle is fully open or fully closed.
Set the throttle lever linkage so that the throttle ro-
tor is (a) fully open when the transmitter throttle
stick is fully advanced and (b) fully closed when
the throttle stick is fully retarded.
Adjustment of the throttle rotor opening at the idling
position can then be made with the throttle trim lev-
er on the transmitter.
(Select throttle-lever and servo-horn hole positions
that will avoid excessive pushrod travel causing the
throttle to bind at either end.)
THROTTLE LINKAGE
When adjusting the throttle lever angle, relative to
the rotor,hold the rotor at about half-way between
the open and closed positions while loosening
and tightening the fixing screw, otherwise the
rotor, rotor guide screw,throttle stop screw or
carburettor body may become burred and
damaged.
Note:
•
•
E-4010 Silencer
11

Suggested fuel tank capacities are listed opposite.
These will allow 12-13 minute flights.
Locate the fuel tank so that the top of the tank is 5-
10mm (1/4-3/8") above the level of the needle-valve.
Be sure to use a pressurized fuel system by
connecting the muffler pressure nipple to the vent-
pipe of the fuel tank.
Suggested Fuel Tank Capacities
50SX
40¡46FX approx 300cc approx 350cc
approx 450cc
61FX
91FX
FUEL TANK LOCATION
Attention to tank height
•
Fuel level
10mm
Model engines generate considerable heat.
Do not touch any part of your engine until
it has cooled.
Contact with the muffler (silencer), cylinder
head or exhaust header pipe, in particular,
may result in a serious burn.
Keep your hands and face away from
exhaust gas or you will suffer a burn.
Reminder!
12

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,therebycontinuingtokeep theenginerunning.
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.
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.
•
•
•
•
•
•
•
•
Glowplug life
Particularly in the case of very high performance
engines,
glowplugs must be regarded as expendable
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.
Recommended O.S. plugs are Nos. 8, A5 and A3.
Carefully install plug finger-tight, before final tighten-
ing with the correct size plug wrench.
GLOWPLUG
13

FUEL
PROPELLERS
Suggested propeller sizes are listed on page 15. The
suitability of the prop depends on the size and weight
of the model and type of flying. Determine the best
size and type after the engine has been run in. Check
the balance of the propeller before fitting it to the
engine. Unbalanced propellers cause vibration and
loss of power. Wooden propellers are to be preferred.
Some nylon propellers are not strong enough to
withstand the high power output of these engines
and a thrown blade can be very dangerous.
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 flam-
mable. 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.
Select, by practical tests, the most suitable fuel from
among the best quality fuels available in your country
for model use. For the best performance, a fuel
containing 5% to 20% nitromethane is preferable.
Lubricants may be either castor-oil or a suitable
synthetic oil ( or a blend of both ) provided that they
are always of top quality.
For consistent performance and long engine life, it is
essential to use fuel containing AT LEAST 18%
lubricant by volume. Some fuels containing coloring
additives tend to deteriorate and may adversely affect
running qualities.
Once a satisfactory fuel has been selected and used
for a while, it may be unwise to needlessly change
the brand or type. In any engine, a change of fuel
may cause carbon deposits in the combustion
chamber or on the piston head to become detached
and lodged elsewhere, with the risk of this causing
unreliable operation for a while. If, however, the
adoption of a different fuel is unavoidable, check the
engine for the first few flights on the new fuel, by
temporarily reverting to the running-in procedure.
Reminder!
Reminder!
14

MIXTURE CONTROLS
50SX
40FX
46FX
61FX
91FX
RING
10✕6,10.5✕6,11✕6 ~ 7
10.5 ✕ 6,11 ✕ 6 ~ 8,12 ✕ 6 ~ 7
12 ✕ 6 ~ 8,13 ✕ 6 ~ 7
15
✕ 8,16 ✕ 6 ~ 8,17 ✕ 6
14
✕ 7 (3-blade)
Sport
13 ✕ 11 ~ 13,14 ✕ 10 ~ 11
11 ✕ 8 ~ 10,12 ✕ 7 ~ 9
(
tuned silencer used
)
12 ✕ 9 ~ 11
(
tuned silencer used
)
Aerobatic
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!
The Needle Valve (at rear of engine)
When set to produce maximum power at full
throttle, this establishes the basic fuel/air mixture
strength. The correct mixture is then maintained by
the carburetor's built-in automatic mixture control
system to cover the engine's requirements at
reduced throttle settings.
The Mixture Control Valve (carburetor)
This meters fuel flow at part-throttle and idling
speeds to ensure reliable operation as the throttle
is opened and closed. The Mixture Control Valve is
factory set for the approximate best result. First run
the engine as received and readjust the Mixture
Control Screw only if necessary.
Two mixture controls are provided on these
engines.
•
•
Type of Carburetor
50SX
40¡46FX 40B 61FX
91FX
60C
60F
11✕6 ~ 10,12✕612✕7
~ 9
15

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.
2 Glowplug
O.S. No.8 glowplug is fitted to the engine.
3 Propeller
Suggested size is 10x6(40FX), 11X6 (46FX), 12X6
(50SX, 61FX), or 15x8(91FX) .
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)
Never touch the nichrome wire while the battery is
connected.
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 element
will overheat and burn out.
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). Battery leads
5 Battery leads
These are used to conduct current
from the battery to the glowplug.
Basically, two leads, with clips, are
required, but, for greater conve-
nience, twin leads with special glowplug connectors,
as shown on the right, are commercially available.
16

12V Battery
Starter
6 Fuel tank
Forinstallationinthemodel,a300cc(10.6oz.)for50SX
and 40,46FX, a 350cc (12oz.) for 61FX, a 450cc
(15.8oz.) for 91FX tank, is suggested.
7 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
fuelpumpsmaybeusedtotransfer
fuel directly from your fuel
container to the fuel tank.
Fuel bulb
Manual
Electric
Fuel pumps
An electric starter is recommended
for starting.
8 Electric starter and starter battery
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.
Fuel Can Filter
10 Silicone tubing
This is required for the
connection between the fuel
tank and engine.
11 Plug wrench
Used for tightening glowplug. The
O.S. long plug wrench is available
as an optional accessory. For tightening
glowplug
STARTING
Install appropriate propeller and tighten securely.
To facilitate electric starting, Install an O.S. solid
aluminium alloy spinner-nut for centering the rubber
drive insert of the starter. Alternatively, a good
quality spinner, enclosing the propeller boss, may be
used, but make sure that it is of precision-made and
sturdy construction so that the spinner shell cannot
loosen when the starter is used. Close the throttle.
1.
2.
17

6. Connect battery leads to glowplug.
Bring electric starter into contact with spinner-nut
or spinner and depress starter switch for one or
two seconds. Repeat if necessary.
When the engine starts, withdraw the starter im-
mediately.
7.
Attention :
Do not choke the carburettor air intake when applying
the starter. This could cause an excessive amount of
fuel to be drawn into the cylinder which may initiate
an hydraulic lock and damage the engine.
If the engine does not start within 10 repeat
applications of the starter, remove the glow-plug,
check that it glows brightly and that the cylinder is not
flooded with fuel. (To eject excess fuel, close needle-
valve and apply starter with glowplug removed.) Then
try again.
VERY IMPORTANT!
Before being operated at full power (i.e. at full-throttle and
with the needle-valve closed to its optimum setting) the
engine must be adequately run-in, otherwise there is a
danger of it becoming overheated and damaged.
Fill the fuel tank. Do not allow fuel to overflow into
the silencer, otherwise the engine may become
flooded and difficult to start.
Check that the needle-valve is closed. (Do not
overtighten.) Now open the needle-valve counter-
clockwise to the starting setting:-
1
~ 2 turns for 50SX,40,46,61FX
2
~ 2 turns for 91FX
3
~ 4 turns for 61FX when a tuned silencer is used.
2
1
2
1
3.
4.
•
•
•
5. Open the throttle approx. one-quarter.
(This is to avoid unnecessarily
high r.p.m. when the engine starts.)
Turn needle-valve clockwise to close
(for leaner mixture)
Turn needle-valve counter-clockwise
to open (for richer mixture)
Mark
Close
Open
Fully closed
position Fully opened position
Set at this point
1
4
3
4
18

RUNNING-IN ("Breaking-in")
All internal-combustion engines benefit from extra
care when they are run for the first few timesknown
as running-in or breaking-in.
This allows the working parts to mate together under
load at operating temperature. Therefore, it is vitally
important to complete the break-in before allowing the
engine to run continuously at high speed and before
finalizing carburetor adjustments.
However, because O.S. engines are produced with
the aid of the finest modern precision machinery and
from the best and most suitable materials, only a
short and simple running-in procedure is called for
and can be carried out with the engine installed in the
model. The process is as follows.
Install the engine with the propeller intended for
your model. Open the needle-valve to the advised
starting setting and start the engine. If the engine
stops when the glow plug battery disconnected,
open the needle-valve to the point where the en-
gine does not stop.Run the engine for one minute
with the throttle fully open, but with the needle-
valve adjusted for rich, slow "four-cycle"operation.
1.
Now close the needle-valve until the engine
speeds up to "two-cycle"operation and allow it to
run for about 10 seconds, then reopen the needle-
valve to bring the engine back to "four-
cycle"operation and run it for another 10 seconds.
Repeat this procedure until the fuel tank is empty.
Re-start and adjust the needle-valve so that the
engine just breaks into "two-cycle" from "four-
cycle" operation, then make three or four flights,
avoiding successive "nose-up" flights.
During subsequent flights, the needle-valve can be
gradually closed to give more power.
However, if the engine shows signs of running too
lean, the next flight should be set rich. After a total
of ten to fifteen flights, the engine should run
continuously, on its optimum needle-valve setting,
without loss of power as it warms up.
After the completion of the running-in adjust the
carburetor at optimum setting referring to
MIXTURE CONTROL VALVE ADJUSTMENT
section and SUBSEQUENT READJUSTMENT
section.
2.
3.
4.
5.
19