91sxh C Spec P Manual

User Manual: 91sxh-c-spec-p-manual

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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.

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 model, radio control equipment, etc.,

are accessible for checking at the same time.

CONTENTS

SAFETY INSTRUCTIONS AND

WARNINGS ABOUT YOUR O.S. ENGINE

NOTES ON INSTALLING,

COOLING-FAN AND CLUTCH

NOTES ON INSTALLING THE ENGINE,

NOTES ON HEATING THE GLOW PLUG

INTRODUCTION

BASIC ENGINE PARTS,

INSTALLATION OF THE CARBURETOR

INSTALLATION OF THE ENGINE

ABOUT THE PUMP SYSTEM

CARE OF FUEL PUMP

FUEL TANK AND PIPING

BEFORE STARTING

2-5

16-18

20-21

FACTS ABOUT GLOWPLUG

CARBURETOR CONTROLS

STARTING, RUNNING-IN ("Breaking-in")

ADJUSTMENT

SUBSEQUENT READJUSTMENTS

CARBURETOR CLEANLINESS

ADJUSTMENT CHART

INSTALLATION OF THROTTLE SERVO

CARE AND MAINTENANCE

EXPLODED VIEW & PARTS LIST

O.S. GENUINE PARTS & ACCESSORIES

THREE VIEW DRAWING

MEMO

13-16

22-24

24-27

32-35

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.

WARNINGS

Never touch, or allow any

object to come into contact

with, the rotating parts.

Model engine fuel is poison-

ous. 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.

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 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.

NOTES

These engine were designed for model

helicopters. Do not attempt to use it for any

other purpose.

Mount the engine in your model securely, fol-

lowing the manufacturers' recommendations,

using appropriate screws and locknuts.

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.

Check the linkage to the throttle arm before

each flight.

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.

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.

Use an electric starter. The wearing of safety

glasses is also strongly recommended.

Press the rotor head down securely.

Take care that the glow plug clip or battery

leads do not come into contact with rotating

parts.

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.

NOTES

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! lmmediately 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.

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.

It is recommended to use Crankshaft

Clamp 7091 (Code No.71530500) available

as an optional tool.

It is made of durable engineering plastic

and locks the crankshaft without risk of

damage to any part of the engine.

Application is as follows:

Remove the crankcase rear cover plate from the

engine and rotate the crankshaft to the bottom

dead center (BDC) position.

Insert the crankshaft clamp so that its grooved

portion surrounds the crankpin and lower end of

the connecting rod and securely tighten the fan

or clutch onto the crankshaft.

Insert this groove onto

the connecting rod.

BDC position

Rotate the crankshaft so that the

connecting rod comes to this position.

Note on installing the engine Note on heating the glow plug

Cooling fan cover from some

helicopter models interferes the

heatsink head.

In this case, cut out the cover as

illustrated.

Example

Cut out according to the heatsink head.

Heatsink head, crankcase and cover

plate of the engine are treated with

Alumite which does not conduct

current. Therefore, when heating a

glow plug, connect one lead to the

glow plug and the other to the head

of cover plate fitting screw.

Example

Because of initial tightness, 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, however, confuse tightness

with the symptoms of hydraulic lock

caused by an excess of fuel within the

cylinder - often the result of over-

priming.

Attempting to force the engine to turn

over in this condition may cause

internal damage. Instead, remove the

glowplug, invert the engine and eject

surplus fuel from the combustion-

chamber.

Note:

This is a pumped version of the 91SX-H

RING C Spec. Pump and muffler

pressurized fuel system ensure stable fuel

supply irrespectire of model attitude and

fuel level in the tank. Return system in the

carburetor ejects the excess fuel and

avoids getting rich at around idling. Easy to

adjust single needly Type 60M carburetor

incorporates a check valve which controls

the fuel supply at any r.p.m. range.

INTRODUCTION

As delivered, the carburetor is not fit to

the engine.

Standard accessories

Glow Plug No.8 Woodruff Key

Needle Adjusting Screw (M2.6x5 1pc.)

Silicone tube

Note:

Carburetor Complete 60M

T nipple

Instruction manual

( 2.5x 5.5xL300mm)

BASIC ENGINE PARTS

Heatsink Head

Carburetor

Typr 60M

Crankshaft

Propeller nut

Crankcase

Thrust Washer

Glowplug

Beam Mount

Pump

As delivered, the carburetor is not fit to the engine.

Secure it as follows.

INSTALLATION OF THE CARBURETOR

Retainer Nut

Carburetor Rubber

Gasket

0.2mm gap

Loosen the retainer nut, press the carburetor well

down into the intake boss, compressing the rubber

gasket as shown in the sketch, before re-tightening

Nut.

Rotate the retainer nut gently until it stops, then

tighten a further 90-120 degrees. Do not over-

tighten the screw as this will damage the carburetor

body.

Pump Holder

60M One-way Valve

Return Screw

Cover Plate

Press down until the gasket becomes almost invisible.

INSTALLING THE GLOWPLUG

Install the washer on the

glowplug and screw

carefully into cylinder-

head, making sure that it

is not cross-threaded

before tightening firmly.

Glow plug

Washer

INSTALLATION OF THE ENGINE

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.

Front view

CORRECT

Side view

Top surfaces are in the same plane.

Re-align the surfaces as necessary

INCORRECT

Top surfaces are not

in the same plane. Top surfaces are not in the

same plane.

Engine does not rest firmly.

Make sure that only the under-

surfaces of the engine’s mounting

lugs are in contact with the engine

mount.

ABOUT THE PUMP SYSTEM

Please understand the pump construction before

piping.

Pump functions in accordance with the engine

r.p.m. Rotating the engine by an electric starter

without connecting battery to a plug sucks fuel.

Prolenged this action may result in over priming.

Attempt to start the engine with over-priming may

result in bending a connecting rod and damaging

the engine.

NOTE:

Fuel is pumped from the tank and delivered to the

carburetor. Set the main needle a little rich at early

stage.

With this system the pump delivers the fuel at

constant pressure even at idling. Then,

unconsumed fuel is returned to the tank ria one-

way valve which avoids getting rich at around

idling.

If the main needle is set correctly, fuel return will

stop at around 60% throttle opening. Therefore, in

the high air flight that requires wider throttle

opening the engine runs under the effects of

muffler pressure, pump pressure and main needle.

During hovering that requires around half throttle

the engine runs under the effects of muffler

pressure, main needle, mixture control and retur

fuel volume.

CARE OF FUEL PUMP

NEVER disassemble the fuel pump or pressure

regulator. Their original performance may not be

restored after reassembly.

NEVER insert anything into the inlet or outlet

nipples in an attempt to clear a suspected

obstruction.

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 pump. Remember to inspect

filter screens at regular intervals and rinse clean as

necessary.

Do not clean the pump with organic solvent such

as kerosene, light machine oil, gasoline, thinner or

crc or the silicone rubbur parts inside is

detoriorated. Be sure to use methanol or fuel.

Do not more the pump adjusting screw at the

center a the adjustment gets out of order and the

parts inside is damaged.

Do not remain fuel in the pump. After finishing the

day's flight session, be sure to use out the fuel in

the pump. Stop the fuel flow to the pump with the

stopper and run the engine at idling to use out the

fuel in the pump. After stopping the engine, rotate

the engine by electric starter to eject fuel inside the

engine.

Pressure adjusting screw

IN OUT

FUEL TANK AND PIPING

Install the engine and a muffler according to the

instructions supplied with the model. Then, connect

piping between tha muffler and fuel tank for muffler

pressurized fuel feed. Then, cut the silicone tube

supplied to 96mm and connect the pump and

carburetor with it.

Pump has fuel flow direction as shown in the sketch.

Be sure to connect between out nipple and carburetor

inlet nipple.

Next, connect piping from one-way valve for fuel

retur. There are two ways.

To return the fuel to the tank.

Connect between one-way valve and fuel tank. Fit a

nipple on the tank. This system ensures stable fuel

supply even with the 3D flight which requires

successire big throttle works.

Clear the burr, if any, off the hole to fit the nipple

with a cutter knife. Also clean the tank with

methanol to remove the dust or tank cut-off

particle.

Fuel tank

Commercialy

available nipple

Nut

Washer

To return the fuel to the tank

muffler pressure

Silencer

Fuel tank

Fuel flow

Pump

Commercialy

available nipple

2. To return the fuel in front the pump

using the T nipple.

muffler pressure

Silencer

Fuel tank

Fuel flow

Pump

In this case, fitting an additional nipple on the tank is

not required. However, pumped out fuel pressure is

increased, and the main needle needs to be closed

further, which results in a sensitive needle reaction

and mixture gets lean at halh throttle with some

types mufflers. In this case, it is suggested to use

yhe pattern 1.

T nipple

BEFORE STARTING

Tools, accessories, etc.

The following items are necessary for operating the

engine.

1 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.

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.

Reminder!

The pump requires running-in as with the engine. Be

sure to check the silicone tubes and connections

carefully for any cracks on the tubes and loose

connections as the engine runs ejecting excess fuel.

4 Glowplug battery

The power source for heating the glowplug may be

either a large heavy-duty 1.5volt dry cell, Ni-cd battery

or battery integrated booster.

1.5 volt dry cell

2 Glowplug

O.S. No.8 glowplug is installed in the engine.

3 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.

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.

Battery Integrated booster

Battery leads

Make sure glowplug element

glows bright red inside room

or shadow.

Battery leads

12V Battery Starter

6 Electric starter and starter

battery

An electric starter is recom-

mended for starting.

5 Hexagon starting shaft

This shaft mounted on an

electric starting motor is driven

into the shaft cup to turn the

engine.

In case of 1.5volt dry cell

10 Plug wrench

Used for tightening glowplug. The

O.S. long plug wrench is available

as an optional accessory.

7 Fuel pump

For filling the fuel tank 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.

For tightening

glowplug

Manual

Electric

Fuel pumps

Fuel Can Filter

8 Fuel container filter

Install a filter on the outlet tube of your

refuelling container to prevent entry of

foreign matter into the fuel tank

9 Silicone tubing

This is required for the connection

between the fuel tank and engine.

ID 2.5mm and OD 5-5.5mm one

would be suitable.

Silicone tubing

2x 5xL12mm

Silicone Tube

Joint Nipple

(Joint nipple and silicone tube are fit

on the cover plate.)

If the silicone tube on the cover plate is damaged,

use commercially available 2mm ID and 5mm OD

silicone tube by cutting to 12mm length.

FACTS ABOUT GLOWPLUGS

The role of the glowplug

Glowplug life

Particularly in the case of very high performance

engines,

glowplugs must be regarded as expendable

items.

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.

Since the compatibility of glowplug and fuel may have

a marked effect on performance and reliability, it may

be worthwhile to choose the R/C type plug found

most suitable after tests. Recommended O.S. plugs

are No.8 and A5. Carefully install plug finger-tight,

before final tightening with the correct size plug

wrench.

Install a plug suitable for the engine.

Use fuel containing a moderate percentage of

nitromethane.

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.

CARBURETOR CONTROLS

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.

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.

The Idle Mixture Control Screw

This provides the means of manually adjusting the

60K's 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.

Two adjustable mixture controls are incorporated in the

Type 60M. They are as follows.

Idle MIxture Control Screw

High Speed Needle Valve

(Main Needle)

Needle

Adjusting screw

As the idle mixture control screw is applied with LOC-

TITE, at first times it is felt stiff, and it is suggested to

use a littli 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.

NOTE

90 degrees

one-way valve

BASIC POSITION OF MIXTURE CONTROL VALVE

(Mixture Control Screw)

Thick

Mixture Control Valve

MIxture Control Screw

Lean

With a model helicopter, adjustments may vary due to

various factors such as climatic conditions, fuel,

muffler, main rotor, weight of the model, gear ratio, etc.

89 degrees

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.

Graduations on the carburetor body

Carburetor Rotor

Carburetor Body

Fully closed

position

Fully opened position

HEX KEY NEEDLE ADJUSTMENT

The knurled head of the main needle valve (High-Speed)

is provided with diagonal slots for use with a screwdriver.

Alternatively, formore positive location via an Allen

hexagonal key, these heads also have M2.6 internal

threads, into which M2.6x5mm Allen cap-head screw

may be fitted. To avoid risk of damage to the fuel

passages when tightening these screws, remove the

needle valves from the carburetor and use 'Loctite'

thread-lock compound to secure the screw.

As delivered, the Mixture

Control Screw is positioned

at 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.

Therefore, the Mixture Control Screw position will

vary with each model and set- up, and it is normal if

the Mixture Control Screw position is off center.

As shown in the sketch,

the carburetor has

graduation marks.

STARTING

Open

Be sure to use a muffler pressurized fuel feed. Use

the same fuel as you intend to employ for actual

operation of your model.

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.

High Speed needle-valve:

exactly two 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.

Checking the rotating direction of the starter

Make sure that the starter rotates

to the direction shown in the

sketch. If the direction is reverse,

reverse the leads on battery.

Inserting the starter shaft

Insert the starting shaft into the

shaft cup securely.

Priming

Without energizing the glowplug,

open the throttle a little from the

idling position. Turn the engine

over using the starter until the fuel

is seen to reach carburetor.

3. Preparation of the starter

Install the starting shaft to the

starter securely.

Improper installation will allow the

shaft to swing creating a

dangerous situation.

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.

Stopping the engine

Fully pull down the throttle trim on the transmitter.

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.

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. 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.

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

come into contact with, the rotating

rotor.

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 is 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. For the first few flights with a new engine i.e.

while the engine is being run-in set the needle-

valve for a slightly rich mixture not excessively rich

as this may result in poor throttle response and cause

the engine to stope. About one half turn open from

the nomal setting will usually suffice.

RUNNING-IN ("Breaking-in")

ー

ADJUSTMENT

Please observe the following before beginning to

make any adjustment.

High-Speed Needle Valve. Turn this approximately

30 degrees (3 to 4 click) at a time, when making

initial adjustments; then in steps of approximately

15 degrees (1 to 2 clicks) when making final

adjustments.

Idle Mixture Control Screw. Turn approximately 10

degrees at a time. It turns approximately 90

degrees both side from the center. Turn left to

enrich the idle mixture and turn right to lean the idle

mixture.

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.

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.

This carburetor is not equipped with a throttle

stop screw. Instead, idling speed is adjusted

by means of the throttle trim lever on the

transmitter.

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. lf, 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 10 degrees. lf 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.

This condition may also be initiated by an

excessively prolonged warming-up period. lf, on

the other hand, the mixture is too Iean, this wiIl be

indicated by a marked lack of exhaust smoke and

a tendency for the engine to cut out when the

throttle is opened. ln this case, turn the Mixture

Control Screw counter-clockwise 10 degrees to

enrich the mixture.

ADJUSTMENT PROCEDURE

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. lf the

engine smokes excessiveIy 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 NeedIe

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.

lf, on the other hand, hovering is not stable and

response to the throttIe 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.

2. After about 10 seconds of idling, open the throttle to

'float' the model. lf the transition is smooth, the idle

mixture is O.K. If the symptoms of either rich or Iean

running are

observed, readjust the Idle Mixture

Control Screw accordingly.

When satisfactory hovering flight has been achieved,

land the modeI again and re-check the engine's idle

qualities.

For helicopters, good throttle response at medium

r.p.m. (e.g. hovering speeds) is most important,

since this is a power range widely used in

helicopter flight. The optimum fuel / air nixture

strength at medium speeds is dependent on

obtaining balanced adjustment of both the Needle

Valve and the Mixture Control Valve.

Now adjust the High-Speed Needle Valve to

achieve the best performance when the model is

flying at full throttle. lf, 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.

lf, however, after smoothly acceIerating to

satisfactory high-speed straight and level flight,

power is lost when the model is puIled up into a

climb, the mixture is too lean. ln 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.

If both controls are alreday at their optimum setting,

some modification to these settings may be

necessary to achieve satisfactory mid-range throttle

response, but such readjustments should only be

made within the rarge where idling reliability and high

speed performance are not undnly compromised.

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 dirt and lint that accumulates on the filter

screen.

Finally, occasionally remove the needle-valve holder

from the carburetor as shown in Photo and extract

any remaining foreign matter that may have lodged in

the location shown in the sketch.

Remove this with

an 8mm spanner

Dirt and fbrous matter

mostly accumulate here

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.

ADJUSTING CHART

High Speed Needle Valve - 2 turns opened from fully closed position.

Idle Mixture Control Screw - 2 turns opened from fully closed position.

Start the engine

Warm up the engine

Observe the mixture condition while "floating" the model

Turn the Idle Mixture

Control Screw counter-

clockwise 10 degrees Idling OK

Turn the Idle Mixture

Control Screw

clockwise 10 degrees

Lean mixture Rich mixture

Observe the hovering mixture condition

Open the High Speed

Needle Valve

(Turn counter-clockwise)

Hovering OK

Lean mixture Rich mixture

Close the High Speed

Needle Valve

(Turn clockwise)

Land the model

Idle for approx: 10 seconds, then reopen throttle to

observe transition ("Float" the model)

Idling OK

Lean mixture Rich mixture

High Speed Flight

Lean mixture Rich mixture

High Speed Flight OK

Fine tuning of hovering mixture

Hovering OK

Adjustment completed

Open the High Speed

Needle Valve

(Turn counter-clockwise)

Close the High Speed

Needle Valve

(Turn clockwise)

Fine tuning of idling mixture

Lean mixture Rich mixture

Idling OK

Turn the Idle Mixture

Control Screw

clockwise 10 degrees

Turn the Idle Mixture

Control Screw

clockwise 10 degrees

Turn the Idle Mixture

Control Screw counter-

clockwise 10 degrees

Turn the Idle Mixture

Control Screw counter-

clockwise 10 degrees

INSTALLATION OF THROTTLE SERVO

After the engine is installed in the helicopter, please

observe the following recommendations when linking

the throttle servo to the carburetor.

Locate the servo so that its output arm and the

throttle pushrod are, as close as possible, di-

rectry in line with carburetor's throttle arm, as

shown.

Servo output arm

Throttle control rod A and B should be equal

length. Set the linkage so that the servo output

arm and throttle arm are parallel when the

throttle stick on the transmitter is at middle

position. If differential throttle movement is re-

quired, make necessary adjustment at the

transmitter.

Throttle arm

27mm

CARE AND MAINTENANCE

The minute particles of foreign matter, that are

present in any fuel may, by accumulating and

partially obstructing fuel flow, cause engine

performance to become erratic and unreliable.

O.S. 'Super-Filters' (large and small)are available,

as optional extras, to deal with this problem.

One of these filters, installed in 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 carburetor.

1. 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.

These procedures will reduce the risk of starting

difficulties and of internal corrosion after a period of

storage.

Do not inject after-run oil into the carburetor as this may

cause the O-rings inside the carburetor to deteriorate.

Note:

Do not forget to clean the filters regularly to remove

dirt and lint that accumulate on the filter screens.

Also, clean the carburetor itself occasionally.

At the end of each operating session, drain out any

fuel that may remain in the fuel tank. Next, energize

the glowplug and try ot 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 remaining fuel/oil

residue by rotating the engine with an electric starter

for 4 to 5 seconds while the engine is still warm.

ENGINE EXPLODED VIEW

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.M3.5x10

910

11 12

19 20

2x 5xL12mm

The specifications are subject to alteration for improvement without notice.

ENGINE PARTS LIST

Screw Set

Cover Plate

Gasket Set

Crankshaft

Crankshaft Ball Bearing (Rear)

Crankcase

Crankshaft Ball Bearing (Front)

Thrust Washer

Propeller Nut

Carburetor Retainer Assembly

Carburetor Complete 60M

Connecting Rod

Piston Pin

Cylinder Liner

Heatsink Head

No. Description

Piston Ring

Piston

Piston Pin Retainer (2pcs.)

Woodruff Key

Glow Plug No.8

29054200

29053100

29503400

29053210

27006000

27917000

29505010

29084000

45010002

46120000

26731002

29081719

29051010

27930000

29052100

29514000

29057020

22681953

29057110

29057100

72509000

29513000

71608001

27708200

29084610

Code No.

Needle Adjusting Screw (M2.6x5) (1pc.)

Joint Nipple (No.1)

Holder "O" Ring

Pump Holder

Pump

T Nipple

CARBURETOR EXPLODED VIEW

Type of screw

C...Cap Screw M...Oval Fillister-Head Screw

F...Flat Head Screw N...Round Head Screw S...Set Screw

C.M3x8

1-1

3-1

3-2

3-3

8-1

8-2

8-3

8-4 8-5

8-6

The specifications are subject to alteration for improvement without notice.

CARBURETOR PARTS LIST

No. Description

Code No.

1-1

3-1

3-2

3-3

8-1

8-2

8-3

8-4

8-5

8-6

27381410

22826131

29084200

29084800

27881810

27881800

27881820

45581820

29084100

27881330

27681340

27081900

27981910

24981837

46181940

46181941

26711305

46181950

Ratchet Spring

Needle

Needle Valve Assembly

Fuel Inlet

Rotor Guide Screw

"O"Ring (L) (2pcs.)

Carburetor Body

Mixture Control Valve Assembly

Carburetor Rotor

Throttle Lever Retaining Screw (2pcs.)

Throttle Lever Assembly

Mixture Control Screw

Mixture Control Valve Stopper

Needle Valve Holder Assembly

"O"Ring (L) (2pcs.)

"O"Ring (S) (2pcs.)

"O"Ring (2pcs.)

Needle Valve Holder

29084440

29084500

29015019 Carburetor Rubber Gasket

Return Screw

No. Description

Code No.

One-way Valve

Needle Adjusting Screw (M2.6x5) (1pc.)

(71608001)

(71521000)

(L)

No.8

(71605100)

(72403050)

(71705000)

(55500003)

(27708010)

LONG SOCKET WRENCH

WITH PLUG GRIP

SUPER FILTER

O.S. GLOW PLUGS IN-FLIGHT CONTROL

NEEDLE VALVE

LOCK WASHER

O.S. GENUINE PARTS & ACCESSORIES

DRIVE HUB

CRANKSHAFT

CLAMP

(10set)

Cap Screw Set

M2.6x5

(10pcs. set)

(79871010)

M3.5x10

(79871070)

7091

(71530500)

(For 70SZ-H, 91SX-H)

Needle Adjusting

Screw

(5pcs.)

M2.6x5 (41621100)

THREE VIEW DRAWING

Displacement

Bore

Stroke

Practical R.P.M.

Power output

Weight

SPECIFICATIONS

Dimensions(mm)

14.95 cc (0.912 cu.in.)

27.7mm (1.091 in.)

24.8mm (0.976 in.)

2,000-16,000 r.p.m.

3.1 ps / 15,000 r.p.m.

581g(20.5oz.)

JAPAN

25 4- 4.2

42.5

42.6

UNF 5/16-24

88.7

56.4

43.5

87.4

MEMO

TEL. (06) 6702-0225

FAX. (06) 6704-2722

6-15 3-Chome Imagawa Higashisumiyoshi-ku

Osaka 546-0003, Japan

URL : http://www.os-engines.co.jp

60091420 090301

91sxh C Spec P Manual

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