O.S. engine MAX-105HZ-R User manual

OS ene
MAXx-105HZ-R
Integrated with O.S. Demand Regulator System
INSTRUCTION MANUAL
It is of vital importance, before attempting to operate
your engine, to read the general 'SAFETY
INSTRUCTIONS AND WARNINGS' section on
pages 2-5 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.
e Keep these instructions in a safe place so that you
may readily refer to them whenever necessary.
e It is suggested that any instructions supplied with
the model, radio control equipment, etc., are
accessible for checking at the same time.
OS creme CONTENTS
SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE --------- 2-5 STARTING ---------------------------- 25-28
NOTES
ON
INSTALLING
COOLING-FAN
ANDCLUTCH
----
6-7
RUNNING-IN
("Breaking-in")
----------------
29
NOTES WHEN APPLYING AN ELECTRIC STARTER, ADJUSTMENT ------------------------ 30-34
INSTALLATION OF THROTTLE SERVO-------- 8-9
ADJUSTMENT CHART -------------------- 35
NOTES ON HEATING THE GLOW PLUG ---------- 10
INTRODUCTION, ENGINE PARTS NAME ---- 11-12 CARE AND MAINTENANCE Sas su spissa 36-37
BEFORE STARTING, TROUBLE SHOOTING -------------------- 38-41
INSTALLATION OF THE ENGINE ---------- 13-16 ENGINE EXPLODED VIEW & PARTS LIST ------ 42-43
INSTALLATION OF THE CARBURETOR EXPLODED VIEW & PARTS LIST----- 44-45
STANDARDACCESSORIES -------------- 17-18
O.S. GENUINE PARTS & ACCESSORIES ---- 46-47
ABOUT THE REGURETOR ,
ABOUT THE SILENCER AND PLUMBING ---- 19-21 THREE VIEW DRAWING ------------------- 48
GLOWPLUGS, CARBURETOR CONTROLS ----- 22-24

SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE
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.
Hi The advice which follows is grouped under two headings according to the
degree of damage or danger which might arise through misuse or neglect.
These cover events which These cover the many other
might involve serious (in possibilities, generally less obvious
extreme circumstances, even sources of danger, but which, under
fatal) injury. certain circumstances, may also
cause damage or injury.
° Never touch, or allow any ° Never operate your engine in an en-
object to come into contact closed space. Model engines, like auto-
with, the rotating parts. mobile engines, exhaust deadly carbon-
monoxide. Run your engine only in an
i . . open area.
e Model engine fuel is poison-
ous. Do not allow it to come
into contact with the eyes or Modël engines: generate
mouth. Always store it in a considerable heat. Do not
clearly marked container and touch any part of your
out of the reach of children. engine until it has cooled.
Contact with the muffler
(silencer), cylinder head or
exhaust header pipe, in
particular, may result in a
serious burn.
e 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.

e This engine was designed for model
helicopters. Do not attempt to use it for any
other purpose.
e Mount the engine in your model securely, fol-
lowing the manufacturers’ recommendations,
using appropriate screws and locknuts.
e Install an effective silencer (muffler). Frequent
close exposure to a noisy exhaust (especially
in the case of the more powerful high-speed
engines) may eventually impair your hearing
and such noise is also likely to cause
annoyance to others over a wide area.
e Check the linkage to the throttle arm before
each flight.
e Avoid sudden high r.p.m. immediately after the
engine is started, as the clutch will engage and
you may be struck by the rotor.
e Take care that loose clothing (ties, shirt sleeves,
scarves etc.) do not come into contact with the
rotor. Do not carry loose objects (such as pen-
cils, screwdrivers, etc.) in a shirt pocket from
where they could fall through the rotor disc.
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.
Hold the rotor securely and keep 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 restart when turned
over WITHOUT the glowplug battery being
reconnected. Remember this if you wish to
avoid the risk of accidents.
e After starting the engine, carry out any needle-
valve readjustments after stopping the rotor by
closing the throttle to the lowest r.p.m..
Stop the engine before attempting to make
other adjustments to the carburetor.
e Use an electric starter. The wearing of safety
glasses is also strongly recommended.
Press the rotor head down securely.
e Take care that the glow plug clip or battery
leads do not come into contact with rotating
parts.
e 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.

OS ave
Notes on installing cooling fan and clutch
Do not use a tool which locks piston
when installing a cooling-fan and
clutch, or top of the piston may be
damaged. Also, do not insert a screw
driver or the similar into the exhaust
port.
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It is recommended to use Crankshaft
Clamp 91/105 (Code No.71530520)
available as an optional tool.
With this engine, the cover plate cannot
be removed when the piston is at BDC
due to engine construction.
When it is required to remove the cover
plate, be sure to position the piston at
TDC.
Ô Scone
Notes on installing cooling fan and clutch
Do not grip the engine mounting
beams with a vise, or the crankcase
will be distorted which will result in
engine breaking.
Beam Mount

OS avez
NOTES WHEN APPLYING AN ELECTRIC STARTER
Because of the initial tightness, of the
piston/sleeve assembly a standard
electric starter may have difficulty in
rotating the engine when cold, before
it has been adequately run-in. In this
case, use a high-torque type 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.
OS. come
Linking the throttle servo to the carburetor
Link the throttle servo to the carburetor using the throttle lever supplied.
Throttle control rod A and B should be equal length. Set the linkage so that
the servo output lever and throttle lever are parallel when the throttle stick on
the transmitter is at middle position. Installation hole intervals on the F lever
and on the J lever are different. Decide the lever to use according to the servo
used. Be sure to cut off the unused levers to avoid any interference.
B

@ Sama
Note on heating the glow plug
The heatsink head on the engine is
treated with an anodized finish which
does not conduct current. Therefore,
when heating a glow plug, connect
one lead to the glow plug and the
other to the head or cover plate
retaining screw.
OS. creme
The MAX-105HZ-R has been developed expressly for 90
size helicopter models, equipping the O.S. regulator
system. It's mounting dimension is the same as the
conventional 90 size engines, while the displacement is
increased by 15%. Also, the conventional 90 size models
gear ratio can be used with this engine without any
modification. The regulator system ensures an always
steady fuel supply which is required for 3D flights which
require repeated vigorous attitude changes as well as for
F3C flights which require severe mixture control.
With this system, the fuel tank is pressurized by pressure
generated in the crankcase. The fuel sent by pressure is
regulated by the regulator installed just ahead of the
carburetor, then sent into the engine. The new silencer
PowerBoost 105 has also been developed to match the
105HZ-R, While the conventional 90 size silencers can also
be used with the 105HZ-R.
A large velocity stack is supplied with the engine to be
installed on the 61G carburetor. Cool fresh air is
conducted to the carburetor intake so that the engine can
develop ideal power characteristics.
When the governor function from Futaba GY-701 or GY-
750 gyro is employed, the Futaba BPS-1 Back Plate
Sensor can be installed in a cell on the back plate. By
employing the governor function, more stable flight can
be achieved.
11
Example
INTRODUCTION
The upper left back plate retaining screw may be used for
a battery ground terminal when connecting the glowplug
battery.
Standard accessories
e Glow Plug No.8
e Velocity Stack
Set Screw M3x3
sD
SP
* Head Gasket (0.1mm)
e Check Valve
e Head Gasket (0.2mm)
NX
NOTE
As delivered, the engine has the carburetor
lightly fit into the intake. Secure it changing
the angle according to the model.

OS. creme ENGINE PARTS NAME
Glowplu
Heatsink Head E
Throttle Lever
Carburetor
Typr 61G
High Speed
Z Needle Valve
Mixture Control
Valve Stopper
Reguretor
<
vai
j
N
W
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Thrust
Washer
I
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Cover
Plate
Medium
Speed
x
By
SO
Needle
Valve
j
iis
Crankcase
x
S
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Carburetor Rubber Gasket
Propeller nut
Crankshaft
12
OS amome BEFORE STARTING
Tools, accessories, etc.The following items are In case of 1.5volt dry cell
necessary for operating the engine.
E items necessary for starting
Glow Plug
O.S. No.8 is supplied with the engine.
Battery leads ©
These are used to conduct current Make sure glowplug element
from the battery to the glowplug. glows bright red inside room
Basically, two leads, with clips, are or shadow.
required, but, for greater conve-
nience, twin leads with special
glowplug connectors, as shown on Battery leads Hexagon starting shaft
the right, are commercially available. This shaft mounted on an
electric starting motor is driven
Glowplug battery
into the shaft cup to turn the
The power source for heating the glowplug may be .
either a large heavy-duty 1.5volt dry cell, Ni-cd battery engine.
or glowplug Igniter.
Á Electric starter and starter
— battery
1.5 volt dry cell An electric starter is recom-
glowplug Igniter mended for starting.
13
Starter

@ Saam
Fuel
Select, by practical tests, the most suitable fuel from among
the best quality fuels available in your country for helicopter
use. For the best throttle response, a fuel containing 10% to
30% 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 deterriorate and may
adversely affect running qualities. If in
doubt compare to a fuel known to be good.
Reminder!
Model engine fuel is poisonous. Do notallow
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.
OS ane
E TOOLS
O.S. SPEED Driver Tools
14
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O.S. SPEED Plug Wrench
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Phillips Screwdriver
No.1, No.2, etc.
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15
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.
O.S. Super Filter (Fuel Can Filter)
Install a filter to 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.
Fuel Filter
It is recommended to install a good in-
line filter between the fuel tank and
carburetor to prevent entry of foreign
matter from getting into the carburetor.
Silicone Fuel Line
Heatproof silicone tubing of approx.
5-5.5mm o.d. and 2.5mm i.d. is
required for the connection between
the fuel tank and engine.
Manual
D
Electric
P
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 as
End Wrenches
8mm, 13mm, 14mm, etc.
Needle Nose Pliers

OS arene
The under-surfaces of all O.S. engine beam
mounting lugs are precision machined flat and
exactyly parallel to the engine's horizontal axis. It is
essential that the engine mounts in the model are
also accurately made and aligned. If they are not,
they will cause stress and distortion within the engine
itself, probably resulting in loss of performance and
internal damage.
The recommended screws for securing the engine to
the engine mounts in the model are 4mm or 4-40
steel Allen type. It is also advisable to use lock
washers or LOCTITE to prevent nuts from loosening.
OS arene
E Installing The Glowplug
Z
Install washer on glowplug
and insert carefully into
Heatsink-head, making sure
that it is not cross-threaded
before tightening firmly.
`
Glow plug
Washer —©
16
17
INSTALLATION OF THE ENGINE
( CORRECT
o GF)
Front view Side view
Top surfaces are in the same plane.
INCORRECT
x a
14
=
Top surfaces are not Top surfaces are not in the
in the same plane. same plane.
pA Engine does not rest firmly.
Re-align the surfaces as necessary
Make sure that only the under-
surfaces of the engine’s mounting
lugs are in contact with the engine
w mount.
INSTALLATION OF THE STANDARD ACCESSORIES
E Installation of Velocity Stack
Install the velocity stack supplied on the carburetor
with M3x3 set-screw supplied.
Cut outthe cooling fan duct so that velocity stack man
not interfere the duct.
The velocity stack develops its performance when
it is completely located inside the duct.
About The Head Gasket
The engine is installed with a 0.2mm thick head
gasket at the factory. When a 15% nitro fuel is used,
run the engine as itis. When a 23% or 30% nitro fuel
is used, add 0.1mm or 0.2mm thick gasket for easier
tuning.

OS avez
E INSTALLATION OF THE CARBURETOR
As delivered, the engine has its carburetor lightly
fitted into its intake boss. Secure it as follows.
1. Loosen carburetor retainer screw slightly.
2. Insert the carburetor rubber
gasket on the carburetor
body securely.
Then, insert the carburetor
in the crankcase.
Carburetor Rubber
Gasket
OS avenue
CARE OF REGURETOR
E NEVER disassemble the pressure regulator.
Their original performance may not be restored
after reassembly.
E NEVER insert anything into the inlet nipple in an
attempt to clear a suspected obstruction.
EDO NOT block the five holes on the top of the
regulator, or the regulator may not work properly.
Do not insert a needle or anything into these holes.
EDO NOT allow foreign matter to enter the fuel
system. Dirt inside the regulator, no matter how
small, may obstruct the flow of fuel and prevent a
from working properly.
a
19
Note: In case it is hard to insert the carburetor in
the crankcase, apply oil on the Thermo Insulater.
Do not force it, or damage to the Thermo Insulater
and/or crankcase can occur.
3. Rotate the retainer screw gently until it stops, then
tighten a further 90-120 degrees.
Do not over-tighten the screw as this will damage
the Thermo Insulater.
Carburetor Rubber
Gasket
Retainer screw
0.2mm gap
Ne A
ABOUT THE REGURETOR
E ALWAYS use fuel filters.
Keep the fuel tank scrupulously clean and filter all
fuel as it enters the tank (e.g.via an O.S.'Super-
Filter’ Code No.72403050) and use a good quality
in-line filter between the tank and regulator.
Remember to inspect filter screens at regular
intervals and rinse clean as necessary.
m DO NOT clean the regulator with organic solvent
such as kerosene, light machine oil, gasoline,
thinner or cre as the silicone rubber parts inside
will deteriorate. Be sure to use methanol or fuel.
E DO NOT allow fuel to remain in the regulator.
After finishing the day's flight session, be sure to run
out the fuel in the regulator. Stop the fuel flow to the
regulator with a stopper and run the engine at idle to
use up the fuel in the regulator. After stopping the
engine, rotate the engine by electric starter to
eliminate fuel inside the engine.

OS. creme
It is suggested to use the O.S. PowerBoost 105
silencer which is developed to best Match the 105HZ-
R. Also, the conventional silencers designed for 90
size engines can be used too.
In this case, install the silencer screwing in the M4x15
bolts from the silencer side since the crankcase has
been tapped to accept the bolts is done on the
crankcase.
Carry out plumbing referring to the instructions
supplied with the silencer.
20
ABOUT THE SILENCER AND PLUMBING
e Carry out plumbing referring to a sketch on page 21.
e Connect silicone tubing cut into approx. 10cm to the
nipple on the cover plate.
e Then, connect the check valve supplied with the
engine as sketched (Be aware of the direction.) It is
suggested to install a stopper as shown in the sketch.
e When refueling, remove this stopper to release
pressure in the fuel tank.
e Connect the fuel line to the nipple on the regulator.
e Be sure to equip a commercially available in-line filter
to avoid dust entering the regulator.
Note:
Since the muffler pressurized fuel feed is not used
with this engine, plug the nipple on the muffler or
replace it with a bolt.
@ Sanm
Check valve Fuel Stopper (commercially available) _
N Remove when refuelling on
j=;
a aroaren part should T Nipple (commercial
ace the fuel tank. available)
I a
Check valve
Be aware of direction
Uw SsƏ]szsIIszSIƏSSƏIEIƏINACIIIIIlIlLl⁄lIlçT(lÍí[2]a2alüx Ni Nig al]
a
Fuel tank
Silicone tubing (commercially (OCH
approx.10cm available) `Z Fuel Stopper
Em = 7 (commercially available)
Fuel Filter
Ne (commercially available)
21

OS creme
+, p. Since the glowplug and fuel combination
ay Bor used may have a marked effect on
SY performance and reliability, it would be
worthwhile to experiment with different
plug types. Recommended O.S. plugs are
No.8, No.7 and No.10 (Former 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.
OS ane
With a fixed-wing model, power failure is rarely a
serious threat to the safety of the aircraft since it can
usually glide down to a safe landing. In a helicopter,
on the other hand, it is vitally imporant that the engine
keeps running and that there is a quick and reliable
response to the throttle in order to ensure safe ascent
and descent of the model.
Three adjustable mixture controls are incorporated in the
Type 61G. They are as follows.
A The High-Speed (Main) Needle Valve
When set to produce maximum power at full
throttle, this establishes the basic fuel/air mixture
strength. This is then maintained by the carburetor's
automatic mixture control system to cover the
engine's requirements at reduced throttle settings.
BThe Idle Mixture Control Screw
This provides the means of manually adjusting the
mixture control valve. By setting the Mixture Control
Screw for the best idling performance, the mixture
control valve automatically ensures that fuel is
accurately metered to maintain the correct mixture
strength as the throttle is opened.
22
23
GLOWPLUG
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.:
elnstall a plug suitable for the engine.
e@Use fuel containing a moderate percentage of
nitromethane unless more is essential for racing events.
e@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:
e Filament surface has roughened and turned white.
e Filament coil has become distorted.
e Foreign matter has adhered to filament or plug
body has corroded.
@ Engine tends to cut out when idling.
e Starting qualities deteriorate.
CARBURETOR CONTROLS
C The Medium Speed Needle Valve
This is an extra control that can be brought into
play, if necessary, after adjusting A and B above. It
provides the means of fine-tuning mixture strength
over that all-important part of a helicopter's throttle
range where the model is flying in, or near, the
hovering mode.
ie Idle Mixture Control Screw N
High Speed Needle Valve
(Main Needle)
N Medium Speed Needle Valve J
NOTE
As the idle mixture control screw is installed with
LOCTITE, it may initialy feel stiff, and it is suggested
to use a slightly oversized screwdriver. The screw can
be turned only 90 degrees either way. Do not force to
turn further, or it may break or cause trouble.
90 degrees —— 90 degrees

OS nem
IB BASIC POSITION OF MIXTURE CONTROL SCREW
(Mixture Control Valve)
As delivered, the Mixture Control Screw is
positioned at approximately the center as shown in
the sketch. Mixture gets lean when the Mixture
Control Screw is turned right, while mixture gets
rich when the Mixture Control Screw is turned left.
With a model helicopter, adjustments vary with
combined various factors such as climatic
conditions, fuel, muffler, main rotor, weight of the
model, gear ratio, etc. Therefore the Mixture
Control Screw position varies with each model and
set- up, and it is normal if the Mixture Control Screw
position is off the center.
Mixture Control Screw
Mixture Control Valve
OS. creme
Be sure to use an electric starter to start
the engine.
Never fail to check the tightness of screws
and nuts, especially engine mounting and
moving parts (e.g. throttle lever).
Starting procedure is as follows:
1. Fill the fuel tank with fuel. When filled, prevent the
fuel from flowing into the carburetor with a
commercially available fuel stopper, etc. Release
the stopper before starting the engine.
2. Make sure that plug element glows red, and install
the plug in the cylinder head.
24
25
E GRADUATIONS ON THE CARBURETOR BODY
As shown in the sketch, the carburetor has
graduation marks.
Fully opened position
89 degrees
Fully closed
position
T
Carburetor Body Carburetor Rotor
When the triangle mark on the carburetor rotor meets
the far right mark, the throttle is fully closed. When
the triangle mark meets the top mark, the throttle is
fully open. The range is 89 degrees. You may use
the other three marks as the reference marking of
throttle opening to your preference when hovering.
WARNING!
Never try to check the triangle mark position
while the engine is running and rotor is rotating,
or you may be hit by rotating rotor which results
in serious injury. Stop the engine and rotor
before checking the triangle mark position.
STARTING
/ Element glows when energized.
Replace the plug when the
element does not glow or is
burnt out.
Glow Plug Igniter
x.
WARNING
When checking the plug element hold the plug
with tools, such as pliers, etc.
Do not hold near your face or the fuel remaining
in the filament may burn you.
4

@ Sawa
1. Opening and closing of the Needle-Valve
Turn the needle clockwise to close the needle-
valve, and turn the needle counter-clockwise to
open the needle-valve as shown in the sketch.
ë Idle Mixture Control Screw: N
Close
High Speed
Medium Sgesd A | needle-valve
edium Speed needle-valve:
s. J
2. High Speed needle-valve:
approx. two half turns open from the fully closed
position. (Note: If a different muffler is used, this
setting may require readjustment)
Idle Mixture Control Screw:
at basic position when the engine leaves the
factory.
26
Ô S mong
5. Inserting the starter shaft
Insert the starting shaft into the
shaft cup securely.
6. Priming
Check the movement of all the controls after
switching on both the transmitter and the receiver.
Then, fully open the throttle valve without heating
the plug. Turn the engine with an electric starter
until the fuel comes into the carburetor inlet.
7. Preparation of starting
Make sure that the transmitter
throttle stick is at the fully closed
position and the throttle trim at
center position, and make sure
that idle-up switch on the
transmitter is off.
27
. Preparation of the starter
. Checking the rotating direction of the starter
œ
Medium Speed needle-valve:
one turn open from the fully closed position.
Install the starting shaft to the
starter securely.
Improper installation will allow the
shaft to swing creating a
dangerous situation.
Make sure that the starter rotates
to the direction shown in the
sketch. If the direction is reverse,
reverse the leads on battery.
Hold the rotor head by hand so that rotor cannot
rotate when the engine is Started. Also, steady the
model with a foot on the landing gear skid.
. Starting
Connect the battery to the glowplug and start the
engine by applying the starter. When started, switch
off the starter and withdraw the starting shaft after
making sure the rotation of the starter shaft stops.
Stopping the engine
Fully pull down the throttle trim on the transmitter.

OS. arene
In case the engine does not stop.
Hold the rotor head, and pinch the fuel line to stop the
fuel supply. If it still does not stop, pull off the fuel line
from the carburetor.
It is necessary to readjust the throttle linkage so that
the carburetor rotor is fully closed when the throttle
stick and throttle trim on the transmitter are fully
pulled Down.
NOTE:
If the throttle response is poor or the engine
stops due to a temporarily over-rich mixture im-
mediately after the engine is started, pinch the
fuel line for one or two seconds until the engine
r.p.m. increase and the engine runs steadily.
Reminder!
Never touch, or allow any object to
uN come into contact with, the rotating
rotor.
OS. creme
All internal-combustion engines benefit, to some
degree, from extra care when they are run for the first
few times known as running-in or breaking-in.
This allows the working parts to mate together under
load at operating temperature.
However, because O.S. engines are made with the
aid of the finest modern precision machinely and from
the best and most suitable materrials, only a very
short and simple running-in procedure is required and
can be carried out with the engine installed in the
model.
28
29
RUNNING-IN ("Breaking-in")
e Main needle is set two and half turns open from fully
closed position and the medium speed needle is set
one turn open from fully closed position when the
engine leaves the factory.
e lt is expected with these needle settings the engine
may run rich. During running-in, hover the model
making sure the engine runs rich.
e Also, during running-in since the mixture is rich, you
may feel uneven engine rpm and more fuel
consumption.
e In the next section, needle adjustments to optimum
position from running-in position are explained.
Be sure to run the engine a little on the rich side so
that if will have a long life expectancy.

Ô Saam
Please observe the following before beginning to
make any adjustment.
e High-Speed Needle Valve. Turn this approximately
30 degrees (3 to 4 clicks) at a time, when making
initial adjustments; then in steps of approximately
15 degrees (1 to 2 clicks) when making final
adjustments.
e Medium-Speed Needle Valve. Turn approximately
30 degrees (3 to 4 clicks) at a time.
e Idle Mixture Control Screw. Turn approximately 5
degrees at a time. It turns approximately 90
degrees both sides from the center. Turn left to
enrich the idle mixture and turn right to lean the idle
mixture.
Ô S, ameme
ADJUSTMENT PROCEDURE
As a safety measure, first check the transmitter
controls, including the throttle stick and trim lever
positions, and hold the main rotor securely before
starting the engine.
1. Warm the engine by allowing it to idle for about 30
seconds. If the engine stops, advance the throttle
trim lever slightly to increase the idle rpm.
Then open the throttle sufficiently to ‘float! the
model above the ground. If, at this time, 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 5 degrees. If the mixture
is extremely 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.
30
31
ADJUSTMENT
The general course of adjustment procedure is
shown in the ADJUSTING CHART and is correct
for a fuel containing 20% lubricant and 15-30%
nitromethane.
Bear in mind that fuels containing relatively large
percentages of power-boosting nitromethane operate
at richer mixture settings than are needed for mild
fuels and will, therefore, require the High-Speed
Needle Valve to be readjusted accordingly. The type
and percentage of lubricant used is also a factor
here, as noted later in these instructions.
This carburetor is not equipped with a throttle
stop screw. Instead, idle speed is adjusted by
means of the throttle trim lever on the trans-
mitter.
This condition may also be initiated by an excessively
prolonged warming-up period. 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 5 degrees to enrich the mixture.

OS arama
2. Having provisionally set the idle mixture, the next
step is to adjust the mixture for hovering flight.
Hover the model and actuate the throttle to observe
response over the medium speed range. If the
engine smokes excessively and throttle response is
poor, the mixture is too rich ; in which case, land the
model and turn the High-Speed Needle Valve
clockwise. Do not close the High-Speed Needle
Valve more than the recommended initial
adjustment (3 to 4 clicks) at a time, keeping it a little
on the rich side at this stage. DO NOT touch the
Medium Speed Needle Valve.
If, on the other hand, hovering is not stable and
response to the throttle is over-sensitive, or if the
engine tends to overheat, this indicates that the
mixture is too lean and should be corrected by
turning the High-Speed Needle Valve counter-
clockwise.
When satisfactory hovering flight has been achieved,
land the model again and re-check the engine's idle
qualities.
OS creme
3. Now adjust the High-Speed Needle Valve to
achieve the best performance when the model is
flying at full throttle. If, at full throttle, acceleration
is poor, the exhaust unduly smoky and the model
fails to reach expected straight line speed, the
mixture is too rich and the High-Speed Needle
Valve setting will need to be reduced.
If, however, after smoothly accelerating to
satisfactory high-speed straight and level flight,
power is lost when the model is pulled up into a
climb, the mixture is too lean. In this case, land the
model immediately and readjust thw High-Speed
Needle Valve to a richer setting.
4. Having now found the optimum setting for the
High-Speed Needle Valve, re-check the engine's
idle performance, fine tuning the Idle Mixture
Control Screw, if necessary, to perfect the idle.
32
After about 10 seconds of idling, open the throttle to
‘float’ the model. If the transition is smooth, the idle
mixture is O.K. If the symptoms of either rich or lean
running are observed, readjust the Idle Mixture
Control Screw accordingly.
= Needle Valve too N
Ë far open
3 !Adjustment range of Medium High Speed Needle
5 Speed Needle Valve Valve Setting varies
according to the curve.
n Needle Valve too
s far closed
=
°
=
š |
5
š LL
5 Z= Control Screw ;
Fully Closed 18 23 Fully Open
Throttle Opening A
NOTE: With this carburetor, neither the Idle
Mixture Control Screw adjustment, nor the
Medium Speed Needle Valve adjustment will have
any effect on mixture strength when the throttle is
fully (or almost fully) open.
5. Now re-check hovering performance It may be
found that (with the High-Speed Needle Valve
now set for optimum full-throttle performance)
hovering will reveal symptoms of slightly lean
running at medium speeds. DO NOT touch the
High-Speed Needle Valve.
It is at this point that the Medium Speed Needle
Valve, previously set one and a half turns open,
may be brought into operation. Open the Medium
Speed Needle Valve 30 degrees, or 3-4 clicks,
then fine tune until the optimum hovering
performance is obtained. If on the other hand,
hovering reveals rich running, close the Medium
Speed Needle Valve gradually until the optimum
hovering performance is obtained.
33

Ô Smene
E SUBSEQUENT READJUSTMENTS
Once the engine has been run-in and the carburetor
controls properly set up, it should be unnecessary to
alter the mixture settings, except to make minor
changes to the Main (High-Speed) Needle Valve
occasionally, to take account of differences in climatic
condisitions.
However, as previously mentioned, the use of a
different fuel, particularly one containing more, or
less, nitromethane and / or a different type or
proportion of lubricating oil, is likely to call for some
modification to the High-Speed Needle-Valve
adjustment.
As a safety measure, it is advisable to increase the
High-Speed Needle Valve setting by an extra half-
turn counter-clockwise, prior to establishing the 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
Needle-Valve setting.
The use of a different glowplug, or changes to the
main rotor and its pitch angles may also require
compensating carburetor readjustments.
34
E CARBURETOR CLEANLINESS
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. It is recommended
that fuel is passed through a filter when the tank is
filled and that a good in-line filter is installed between
the fuel tank and carburetor and, furthermore, that
this filter is frequently cleaned to remove foreign
matter that accumulates on the filter screen. Finally,
occasionally remove the needle-valve holder from the
carburetor as shown in Picture and extract any
remaining foreign matter that may have lodged in the
location shown in Picture below.
Remove this with
an 8mm wrench
Dirt and foreign matter
mostly accumulate here
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35

OS cnong
Please pay attention to the matters
described below to ensure that your engine
serves you well in regard to performance,
reliability and long life.
e As previously mentioned, it is vitally important
to avoid operating the engine in conditions
where dust, disturbed by the rotor, may be
deposited on the engine and enter its working
parts.
e Remember to keep your fuel container
closed to prevent foreign matter from
contaminating the fuel.
e Install a fuel filter to prevent foreign matter in
the fuel container from entering the fuel tank.
O.S. Super Filters (L) and (S) are available
as optional extras.
OS avemez
e Do not close the needle-valve and mixture
control valve too far as this will cause a lean
setting and over heating of the engine. This
can, in turn, create nitromethane oxide
leading to internal rusting of the engine.
Always adjust the needlevalve slightly on the
rich side of peak rpm.
e Do not leave unused fuel in the engine at the
conclusion of a day’s flying. Accepted
practice is to cut off the fuel supply while the
engine is still running at full throttle, then
expel as much fuel residue as possible by
turning the engine over 5-10 seconds with
the electric starter.
Finally, inject some after-run oil through the
glowplug hole and turn the engine over
several times by hand.
36
37
CARE AND MAINTENANCE
e Install an in-line fuel filter between the tank
and carburetor to prevent foreign matter in
the tank from entering the carburetor.
e Clean these filters periodically.
e |f these precautions are neglected, restriction
of fuel flow may cause the engine to cut out,
or the fuel/air mixture to become too lean
causing the engine to overheat.
e The use of modern high-performance alcohol
based model engine fuels, while promoting
cooler running, improved anti-detonation
combustion and increased power, have the
disadvantage of causing corrosion due to the
acid by-products of combustion.
The use of nitromethane in the fuel can also
contribute to the problem.
e When the engine is not to be used for some
months (for example, as between flying
seasons), a worthwhile precaution is to
remove it from the airframe and, after
washing off the exterior with alcohol (not
gasoline nor kerosene), remove carefully the
carburetor with intake pipe, glow plug and all
silicone tubing and put them safely aside.
Then, immerse the engine in a container of
alcohol. Rotate the crankshaft while the
engine is immersed. If foreign matter is
visible in the alcohol, rinse the engine again
in clean alcohol. Finally, shake off and dry
the alcohol, and inject some after-run oil in
the glowplug hole and rotate the crankshaft
several times by hand.
Reinstall the carburetor with intake pipe and
glowplug on the engine and keep it in a dry
place after putting in a vinyl bag.

OS menz
TROUBLE SHOOTING
Engine fails to fire.
Cause
Corrective action
Fuel tank is empty.
Fuel not reaching the engine.
Fill the tank with fuel and repeat.
Priming procedure.
Glowplug element is burnt out.
Glowplug battery discharged
Replace glowplug.
Recharge or replace the battery.
Clogged fuel filter. Silencer inside is dirty.
Over priming
Clean or replace fuel filter. Clean inside silencer.
Remove glowplug and pump out excess fuel.
Fuel tubing is disconnected.
Fuel tubing is kinked, split or has a hole.
Connect fuel tubing securely.
Check the tubing carefully and replace if necessary.
Incorrect carburetor settings
Return the needle valve
and mixture control valve to basic position.
Incorrect servo linkage
Reconnect linkage after setting servo at neutral.
Reverse rotating direction of electric starter.
Mare sure the engine rotates counter clockwise
seen from crankshaft side.
@ Saam
38
Engine fires intermittently but does not run.
Cause
Corrective action
Insufficient fuel in the tank. Fill the tank with fuel.
Deteriorated glowplug
Replace glowplug.
Clogged fuel filter
Silencer inside is dirty.
Clean or replace fuel filter.
Clean inside silencer.
Engine overheated
Wait until engine has cooled.
Disconnecting plug battery too soon.
Do not disconnect plug battery and wait until
the r.p.m. becomes stable.
Air bubbles in fuel
Fit O rings to the tank screws to
prevent bubbles.
39