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.
1
CONTENTS
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
2-6
7
8
8-10
10-11
11-12
12
13
14-15
15
16-17
STARTING
17-18
19-21
22
23
24
25
37-38
26-33
34-36
39-42
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 ese co ver ev ents which
mig ht inv olve s erio us (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 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.
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)
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.
5
NOTES
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
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 propell er s for specializ ed
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.
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. Also, check
the tightness of all the screws and nuts
before restarting the engine.
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
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 inser t plug, with
washer, fingertight only, before
final tightening with the correct
size plug wrench.
BEFORE INSTALLING THE ENGINE
Installing the glowplug
Connect the shor t 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
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
8
As delivered from the factory, the MAX-61FX has its
need le-valve a ssembly installed horizontally.
However, if more convenient for a particular
installation, the needle-valve may be reinstalled
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 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.
The proce
dure for relocating the needle-valve vertically
is as follows:
1.
2.
3.
9
Inlet Holder
Plug Screw
Fuel Inlet
Needle-Valve
Assembly
Needle Extension
Inlet Holder
Fuel Inlet
Needle-Valve
Assembly
45mm
Fuel Inlet
Needle-Valve
Assembly
Plug Screw
Fuel Inlet
Needle-Valve
Assembly
Needle Extension
45mm
61FX
50SX
Use hexagon-head brass inlet holder (61FX) or
plug screw (50SX) to blank off side boss vacated
by needle- valve assembly.
4.
As delivered from the factory, the 91FX has the
needle-valve assembly installed vertically. However, if
more convenient for a par ticular installation, the
needle-valve may be reinstalled horizontally.
The procedure for relocating the needle-valve is as
follows:
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.
1.
10
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)
Finally, secure the complete assembly to rear cover
plate as before.
3.
Vertical position
(Factory position)
Horizontal position
Cover plate fitting holes
Needle Valve unit
Needle Valve unit Retaining screws
Needle Stay
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:
Rotate the needle-valve unit through 90˚ and reattach it to the bracket in the required position (see
sketch below).
2.
91FX
11
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 rotor 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 lever on the transmitter. (Select throttlelever and servo-horn hole positions that will avoid excessive pushrod travel causing the throttle to bind at
either end.)
THROTTLE LINKAGE
Note: 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.
The exhaust outlet of the silencer can be rotated to
any desired position in the following manner:
SILENCER
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).
12
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 510mm (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 ventpipe 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!
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.
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
E-4010 Silencer
13
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,
appropriat ely, fir es the fuel/a ir charg e earlie r;
conversely, at reduced rpm, the plug become cooler and
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
items.
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 tightening with the correct size plug wrench.
GLOWPLUG
14
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 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.
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!
15
MIXTURE CONTROLS
50SX
40FX
46FX
61FX
91FXRING
10x6, 10.5x6, 11x6-7
10.5x6, 11x6-8, 12x6-7
12x6-8, 13x6-7
15x8, 16x6-8, 17x6, 14x7 (3-blade)
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.
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
11x7-9, 12x6-7
16
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 supplied with 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
vo
ltage to
increase
br
ightness
.
Lo
wer
vo
ltage to
reduce br
ightness
.
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, o therwise 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 convenience, twin leads with special glowplug connectors,
as shown on the right, are commercially available.
17
12V Battery
Starter
6 Fuel tank
For installation in the model, a 300cc (10.6oz.) for 50SX
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 s pout,is all tha t is
required. Alternatively, one of the
purpose-made manual or electric
fuel pumps may be used to transfer
fue l directly from yo ur fu el
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
Thi s 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.
18
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 immediately.
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 needlevalve 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 counterclockwise to the starting setting:-
1 -2 turns for 50SX,40,46,61FX
4-5 turns for 91FX
3-4 turns for 61FX when a tuned silencer is used.
2
1
3.
4.
5. Open the throttle approx. one-quarter.
(This is to avoid unnecessari ly
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
19
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 engine does not stop.Run the engine for one minute
with the throttle fully open, but with the needlevalve 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 needlevalve to bring the engine back to "fourcycle"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 "fourcycle" 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.
20
Slowly advance the throttle to its fully open position,
then gradually close the needle-valve until the
exhaust note begins to change. (4-cycle to 2-cycle)
At this point, disconnect the battery from the
glowplug, taking care that the battery leads or
glowplug clip do not come into contact with the
rotating propeller. If the engine stops when the
battery is disconnected, close the needle-valve about
30˚ and restart.
As the needle-valve is closed slowly and gradually,
the engine r.p.m. will increase and a continuous highpitched exhaust note, only, will be heard. Close the
needle-valve 10-15˚ and wait for the change of r.p.m.
After the engine r.p.m. increases turn the needlevalve 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.
Optimum needle setting(1)
Optimum needle setting(2)
21
20-45
˚
Needle-valve adjustment diagram
This diagram is for reference
purposes only.
Actual needle positions may
differ from those shown.
To stop the engine, close the
throttle completely to cut off
fuel/air supply.
Note :
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").
STARTING
"Rich" needle-valve
setting when starting
the engine.
The engine may stop if
the battery leads are
disconnected from t he
glow plug while the
engine is running rich.
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
Intermittent, high-pitched
two-stroke note
superimposed
on low "four-stroke"
sound.
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.
1
2
3
4
5
6
7
22
IDLING ADJUSTMENT CHART
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.
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
Refer to the next section.
Re-set the idling position at
a little higher r.p.m.
Set the throt tle open ing b y
means of the t hrottle trim on
the transmitter so that the lowest
practical speed, without risk of
the engine stopping,is obtained.
The position where the lowest
pos sibl e r .p.m. , with st ead y
running, is obtained.
20-30˚ open from maximum
r.p.m. setting.
Yes.
No.
Yes.
Engine stops.
Engine stops.
Disconnect the battery
leads at mid speed.
Engine stops.
23
MIXTURE CONTROL VALVE ADJUSTMENT
REALIGNMENT OF MIXTURE CONTROL VALVE
With the engine running, close the throttle and allow it
to idle for about five seconds, then open the throttle
fully. If, at this point, the engine is slow to pick up and
produces an excess of exhaust smoke, the mixture is
too rich. Correct this condition by turning the Mixture
Control Screw clockwise 15-30˚. If the mixture is
excessively rich, engine rpm will become unstable:
opening the throttle will produce a great deal of
smoke and rpm may drop suddenly or the engine
may stop. This condition may also be initiated by
excessively prolonged idling.
If,on the other hand, the mixture is too lean, this will
be indicated by a marked lack of exhaust smoke and
a tendency for the engine to cut out when the throttle
is opened. In this case, turn the Mixture Control
Screw counter-clockwise 90˚to positively enrich the
idle mixture, then turn the screw clockwise gradually
until the engine regains full power cleanly when the
throttle is reopened.
Carry out adjustments patiently until the engine
responds quickly and positively to the throttle control.
Note: Mixture Control Valve adjustments should
be made in steps of 15-30˚ initially,
carefully checking the effect, on throttle
response, of each small adjustment.
In the course of making carburetor adjustments, it is
just possible that the Mixture Control Valve may be
inadvertently screwed in or out too far and thereby
moved beyond its effective adjustment range.
Its basic setting can be re-established as follows:
Close the throttle rotor gradually from the fully
opened position until it is just fully closed.
(Do not turn further.) Then, screw in the Mixture
Control Screw until it stops. Now unscrew the Mixture
Control Screw as indicated below.
50SX
40, 46FX
approx1 turn
61FX
91FX
approx
turns
approx2
turns
2
1
2
1
2
1
24
SUBSEQUENT STARTING PROCEDURE
SUBSEQUENT READJUSTMENT
Once the optimum needle-valve setting has been established (see page 19, Needle-valve adjustment diagram) the procedure for starting may be simplified as
follows.
Open the needle-valve one half-turn (180°) from
the optimum setting.
Set the throttle one-quarter open from the fully
closed position, energize the glowplug and apply
the electric starter. When the engine starts, reopen the throttle and re-adjust the needle-valve to
the optimum setting.
When re-starting the engine on the same day,
provided that atmospheric conditions have not
changed significantly, it may be practicable to restart the engine on its optimum(running) setting.
Once the engine has been run-in and the controls
properly set up, it should be unnecessary to alter the
mixture settings; except to make minor adjustments
to the Needle-Valve occasionally, to take account of
variations in climatic conditions.
The use of a different fuel, however, particularly one
containing more, or less, nitromethane and/or a
different type or proportion of lubricating oil, is likely to
call for some readjustment of the Needle-Valve.
Remember that, as a safety measure, it is advisable
to increase the Needle-Valve opening by an extra
half-turn counter-clockwise, prior to establishing a
new setting. The same applies if the silencer type is
changed.
A different silencer may alter the exhaust pressure
applied to the fuel feed and call for a revised NeedleValve setting. The use of a different glowplug may
also require compensating carburetor readjustments.
Note:
1.
2.
25
CARBURETOR CLEANLINESS
ENGINE CARE AND MAINTENANCE
At the end of each operating session, drain out any
fuel that may remain in the fuel tank.
Next, energize the glowplug and try to restart the
engine to burn off any fuel that may remain inside
the engine. Repeat this procedure until the engine
fails to fire. Remove the glowplug and eject any residue by rotating the engine with an electric starter
for 4 to 5 seconds while the engine is still warm.
Finally, inject some after-run oil into the engine.
Rotate the engine a few times by hand, to make
sure that it is free, and then with an electric starter
for 4 to 5 seconds to distribute the oil to all the
working parts.
Do not inject after-run oil into the carburetor as
this may cause the O-ring inside the carburettor
to deteriorate.
These procedures will reduce the risk of starting
difficulties and of internal corrosion after a period of
storage.
The correct functioning of the carburetor depends on
its small fuel orifices remaining clear. The minute
particles of foreign matter that are present in any fuel,
can easily partially obstruct these orifices and upset
mixture strength so that engine performance
becomes erratic and unreliable.
O.S.'Super-Filters'(large and small ) are available, as
optional extras, to deal with this problem.
One of these filters, fitted to the outlet tube inside
your refueling container, will prevent the entry of
foreign material into the fuel tank.
It is also recommended that a good in-line filter be
installed between the tank and needle-valve.
Do not forget to clean the filters regularly to remove
dirt and lint that accumulate on the filter screen.
Also, clean the carburetor itself occasionally.
Note:
1.
2.
3.
26
EXPLODED VIEW (50SX)
Type of screw
C...Cap Screw M...Oval Fillister-Head Screw
F...Flat Head Screw N...Round Head Screw S...Set Screw
C.M3x15
C.M2.6x18
C.M3x8
S.M3x3
1
20-10
2
3
4
5
6
7
8
9
11
12
13
14
10
13-1
15
16
17
19
21
18
20
20-1
20-2
20-5
20-3
20-4
20-8
20-6
20-7
20-9
27
ENGINEN PARTS LIST (50SX)
The specifications are subject to alteration for improvement without notice.
Description
Code No.
No.
123456789
101112
13
13-1
14151617181920
20-1
20-2
20-3
20-4
20-5
20-6
20-7
20-8
20-9
20-10
21
25204010
25203100
25303400
25203200
25206000
25217000
25205000
25681010
25281140
23981700
23210007
23209003
27708010
27708200
46120000
26731002
25201000
26730010
25202010
25214000
25207010
25207100
24081970
24981837
26381501
46181940
46181941
26711305
46181950
22881310
22681953
25613000
71608001
25425000
22681957
25425310
25425400
Cylinder Head
Cylinder Liner
Piston Ring
Piston
Piston Pin
Piston Pin Retainer
Connecting Rod
Carburetor Complete (Type 40B)
Carburetor Spacer
Carburetor Retainer
Propeller Nut
Propeller Washer
Drive Hub
Woodruff Key
Thrust Washer
Crankshaft Ball Bearing (F)
Crankcase
Crankshaft Ball Bearing (R)
Crankshaft
Gasket Set
Cover Plate Assembly
Cover Plate Body
Needle Assembly
"O" Ring
Set Screw
Needle Valve Holder Assembly
Needle Valve Holder
Ratchet Spring
Fuel Inlet
Plug Screw
Fuel Outlet (No.1)
Screw Set
Glow Plug No.8
873 Silencer Assembly
Pressure Fitting
Assembly Screw
Retaining Screw (C.M3x35 2pcs.)
28
EXPLODED VIEW (40,46FX)
C.M3x15
N.+M3.5x6
S.M3x3
C.M3x8
1
2
3
4
5
6
6-1
6-2
7
8
9
10
11
12
13
14
15
17
16
16-1
16-2
16-3
16-4
16-5
16-6
16-7
Type of screw
C...Cap Screw M...Oval Fillister-Head Screw
F...Flat Head Screw N...Round Head Screw S...Set Screw
29
ENGINEN PARTS LIST (40,46FX)
Specifications are subject to alteration for improvement without notice.
12345
6
6-1
6-2
789
10111213141516
16-1
16-2
16-3
16-4
16-5
16-6
16-7
17
Code No.
No. Description
25604000
25603000
25406000
24817100
25305002
25681010
46215000
25081700
23210007
23209003
25608000
46120000
26731002
25601000
26730005
25602021
25614000
25607000
25607100
22681953
22681980
24981837
26381501
27381940
26711305
25613000
71608001
25425000
22681957
25425310
25425400
25604010
25603010
24806301
24817100
25305002
25681010
46215000
25081700
23210007
23209003
25608000
46120000
26731002
25601100
26730005
25602021
25614010
25607000
25607100
22681953
22681980
24981837
26381501
27381940
26711305
25613000
71608001
25425000
22681957
25425310
25425400
40FX 46FX
Retaining Screw (2pcs.)
Assembly Screw
Pressure Fitting
873 Silencer
Screw Set
Ratchet Spring
Needle Valve Holder Assembly
Set Screw
"O" Ring
Needle
Fuel Outlet
Cover Plate Body
Cover Plate Assembly
Gasket Set
Crankshaft
Crankshaft Ball Bearing (R)
Crankcase
Crankshaft Ball Bearing (F)
Thrust Washer
Drive Hub
Propeller Hub
Propeller Nut
Carburetor Retaining Screw (2pcs.)
Carburetor Rubber Gasket
Carburetor (Type 40B)
Connecting Rod
Piston Pin Retainer
Piston Pin
Cylinder & Piston Assembly
Cylinder Head
Glow Plug No.8
30
EXPLODED VIEW (61FX)
C.M3x15
N.+M3.5x6
S.M3x3
C.M3.5x8
16-10
1
2
3
4
5
6
13
7
8
9
10
11
12
14
15
17
16-3
16-5
16-4
16-11
16-1
16
16-2
16-9
16-7
16-6
16-8
Type of screw
C...Cap Screw M...Oval Fillister-Head Screw
F...Flat Head Screw N...Round Head Screw S...Set Screw
31
ENGINEN PARTS LIST (61FX)
The specifications are subject to alteration for improvement without notice.
123456789
10111213141516
16-1
16-2
16-3
16-4
16-5
16-6
16-7
16-8
16-9
16-10
16-11
17
27754000
27753000
26606008
27917000
29505000
27783000
45010002
28009002
27758000
29320000
27731000
27751000
29030001
27752000
27914000
27757000
27757100
22681953
27757010
46181950
27757030
22681980
24981837
26381501
27783940
21281800
26711305
27913000
71608001
26028000
22681953
26028100
26625210
Description
Code No.
No.
Cylinder Head
Cylinder Piston Assembly
Piston Pin
Piston Pin Retainers (2pcs.)
Connecting Rod
Carburetor Complete (Type 60C)
Propeller Nut
Propeller Washer
Drive Hub
Thrust Washer
Crankshaft Ball Bearing (F)
Crankcase
Crankshaft Ball Bearing (R)
Crankshaft
Gasket Set
Cover Plate Assembly
Cover Plate Body
Fuel Outlet (No.1)
Fuel Inlet Assembly
Fuel Inlet
Inlet Holder
Needle Assembly
"O" Ring
Set Screw
Needle Valve Holder Assembly
"O" Ring
Ratchet Spring
Screw Set
Glow Plug No.8
E-4010 Silencer Assembly
Pressure Fitting
Assembly Screw
Retaining Screw (C. M4x40 2pcs.)
32
EXPLODED VIEW (91FXRING)
Type of screw
C...Cap Screw M...Oval Fillister-Head Screw T...Tapping Screw
F...Flat Head Screw N...Round Head Screw S...Set Screw
C.M3x15
N.+M3.5x6
C.M3.5x10
1
2
3
4
5
6
7
16
8
9
10
11
12
10-1
15
13
14
20
S.M3x3
18
19
19-1
19-3
19-2
19-4
19-5
19-6
T.+3x10
17
33
ENGINE PARTS LIST (91FX RING)
The specifications are subject to alteration for improvement without notice.
Description
Code No.
No.
Cylinder Head
Cylinder Liner
Piston Ring
Piston
Piston Pin
Piston Pin Retainers (2pcs.)
Connecting Rod
Carburetor Complete (Type 60F)
Propeller Lock Nut Set
Drive Hub
Woodruff Key
Thrust Washer
Crankshaft Ball Bearing (F)
Crankcase
Crankshaft Ball Bearing (R)
Crankshaft
Gasket Set
Cover Plate
Needle Stay
Needle Valve Unit Assembly
Needle Assembly
"O" Ring (2pcs.)
Set Screw
Ratchet Spring
Needle Valve Unit Body
Needle Valve Unit Retaining Screw
Screw Set
Glow Plug No.8
E-4020 Silencer Assembly
Pressure Fitting
Assembly Screw
Retaining Screw (C. M4x40 2pcs.)
Needle Valve Extension Cable Set
123456789
10
10-1
111213141516171819
19-1
19-2
19-3
19-4
19-5
19-6
20
29504000
29503100
29503400
29053200
45406000
27917000
29505000
29581000
45910100
29508000
29008219
46120000
26731002
29501000
29030001
29502000
29514000
29057000
26582931
26582900
24081970
24981837
26381501
26711305
26582910
26582920
29513000
71608001
29525000
22681957
29525100
26625210
72200080
34
CARBURETOR 40B (50SX,40,46FX)
1
1-1
2
3
4
5
6
7
8
N.+M3.5x6
1-2
9
2-1
Type of screw
C...Cap Screw M...Oval Fillister-Head Screw
F...Flat Head Screw N...Round Head Screw S...Set Screw
Description
Code No.
No.
1
1-1
1-2
2
2-1
3
4
5
6
7
8
9
22781401
22781411
22781420
27783600
22781800
25681200
26781506
25681100
25681620
22681953
46215000
25081700
Throttle Lever Assembly
Throttle Lever
Throttle Lever Fixing Screw
Mixture Control Valve
"O"Ring
Carburetor Rotor
Rotor Spring
Carburetor Body
Throttle Stop Screw
Fuel Inlet (No.1)
Carburetor Gasket
Carburetor Retaining Screw
The specifications are subject to alteration
for improvement without notice.
35
CARBURETOR 60C (61FX)
1
1-1
2
3
4
5
6
7
8
N.+M3.5x6
1-2
9
2-1
1
1-1
1-2
2
2-1
3
4
5
6
7
8
9
22781401
22781411
22781420
27783600
22781800
27783200
26781506
27783100
25681620
22681953
46215000
25081700
Type of screw
C...Cap Screw M...Oval Fillister-Head Screw
F...Flat Head Screw N...Round Head Screw S...Set Screw
Description
Code No.
No.
Throttle Lever Assembly
Throttle Lever
Throttle Lever Fixing Nut
Mixture Control Valve Assembly
"O" Ring
Carburetor Rotor
Rotor Spring
Carburetor Body
Throttle Stop Screw
Fuel Inlet (No.1)
Carburetor Gasket
Carburetor Retaining Screw
The specifications are subject to alteration
for improvement without notice.
36
CARBURETOR 60F (91FXRING)
1
2
3
3-1
3-2
4
5
6
7
8
27881400
29581200
45582300
46066319
24881824
29581100
45581820
22681953
29015019
25081700
1
3-1
2
3
4
5
6
7
8
N.+M3.5x6
3-2
N.+M3x6
Type of screw
C...Cap Screw M...Oval Fillister-Head Screw
F...Flat Head Screw N...Round Head Screw S...Set Screw
Description
Code No.
No.
Throttle Lever Assembly
Carburetor Rotor
Mixture Control Valve Assembly
"O" Ring (L)
"O" Ring (S)
Carburetor Body
Rotor Guide Screw
Fuel Inlet (No.1)
Carburetor Gasket
Carburetor Retaining Screw
The specifications are subject to alteration
for improvement without notice.
37
No.8
(71608001)
A5
(71605100)
For 50SX. 40.46FX
73101000
73101010
1/4"-28
5/16"-24
50SX. 40. 46FX
61FX. 91FX
25425600
26625340
26625500
50SX. 40.46FX (873
)
61FX (E-4010
).
91FX (E-4020
)
Length 35mm
61FX (E-4010
).
91FX (E-4020
)
A3
(71605300)
O.S.
GLOW PLUGS
O.S. GENUINE PARTS & ACCESSORIES
SPINNER NUT
23024009
45024000
1/4"-28(L
)
5/16"-24
50SX. 40. 46FX
61FX. 91FX
Code No.
Size
Type of Engine
LONG PROPELLER
NUT SETS
Code No. Size Type of Engine
SILENCER EXTENSION ADAPTORS
Code No.
Type of Engine • Silencer
PROPELLER NUT SETS
FOR TRUTURN SPINNERS
(73101020)
RADIAL MOTOR
MOUNTS
71913100
71905200
50SX. 40. 46FX
61FX. 91FX
Code No.
Type of Engine
(72200080)
NEEDLE VALVE EXTENSION
CABLE SET
25425020
26028010
873S
E-4010S
50SX. 40/46FX
61FX
Code No.
Size
Type of Engine
SUPER SILENCERS
38
(72101230)
For 61FX, 91FX
(72403050)
(71531000)
(72101120)
(71521000)
55500002
55500003
50SX. 40.46FX
61FX.91FX
M3
M4
72105337
72101338
40.46FX
61FX.91FX
For 61FX
EXHAUST
HEADER PIPE
Code No.
Size
Type of Engine
Code No.
Type of Engine
O.S. SILICONE
TUBE ASSEMBLY
SUPER FI LTER
NON-BUBBLE WEIGHT
LOCK WASHER
(10Sets)
LONG SOCKET WRENCH
WITH PLUG GRIP
T-4010 TUNED SILENCER
79870030
79870040
50SX. 40.46FX
61FX.91FX
M3
M4
Size
Code No.
Type of Engine
BLIND NUTS
(10pcs. /Sets)
The specifications are subject to alteration for improvement without notice.
M3.5x8
(79871060)
M3.5x10
(79871070)
CAP SCREW SETS
(10pcs./sets)
39
MAX-50SXRING
Displacement
Bore
Stroke
Practical R.P.M.
Power output
Weight
8.17 cc (0.499 cu.in.
)
22.0mm (0.866 in.
)
21.5mm (0.847 in.
)
2,000-20,000 r.p.m.
1.8 ps / 17,000 r.p.m.
390g (13.76 oz.
)
SPECIFICATIONS
Dimensions(mm)
UNF1/4-28
52
36
44
17.5
60.7 25
18.3
28
70.5
121
7.5
37.7
21
40
MAX
- 40FX
MAX
- 46FX
Displacement
Bore
Stroke
Practical R.P.M.
Power output
Weight
6.47 cc (0.395 cu.in.
)
20.5mm (0.807 in.
)
19.6mm (0.772 in.
)
2,000-17,000 r.p.m.
1.36 ps / 16,000 r.p.m.
386g (13.6 oz.
)
SPECIFICATIONS
Displacement
Bore
Stroke
Practical R.P.M.
Power output
Weight
7.45 cc (0.455 cu.in.
)
22.0mm (0.866 in.
)
19.6mm (0.772 in.
)
2,500-17,000 r.p.m.
1.62 ps / 16,000 r.p.m.
375g (13.2 oz.
)
SPECIFICATIONS
Dimensions(mm)
THREE VIEW DRAWING
17.5
44
UNF1/4-28
60.5
19.5
70
88
35
51
36.3
41
MAX
- 61FX
Displacement
Bore
Stroke
Practical R.P.M.
Power output
Weight
9.95 cc (0.607 cu.in.
)
24.0mm (0.945 in.
)
22.0mm (0.866 in.
)
2,000-17,000 r.p.m.
1.9 ps / 1.93 hp / 16,000 r.p.m.
550g (19.42 oz.
)
SPECIFICATIONS
Dimensions(mm)
43
61
UNF5/16-24
66.5
29.1
43
79
100.5
ø4.2
42
25
ø4.2
52
42
MAX
-
91FX
RING
Dimensions(mm)
Displacement
Bore
Stroke
Practical R.P.M.
Power output
Weight
14.95 cc (0.912 cu.in.
)
27.7mm (1.091 in.
)
24.8mm (0.976 in.
)
2,000-16,000 r.p.m.
2.8 ps / 15,000 r.p.m.
550g (19.42 oz.
)
SPECIFICATIONS
25
4- 4.2
52
81.5
103
21.5
42.6
61
43.5
24.7
66.5 29.5
103.6
UNF 5/16-24
C
Copyright 2001 by O.S.Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan.
60090880 061106
TE L. (06) 6702-0225
FAX. (06) 6704-2722
6-15 3-Chome Imagawa Higashisumiyoshi-ku
Osaka 546-0003, Japan
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URL : http://www.os-engines.co.jp
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