O.S. Engines 91SZ-H User 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.

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.

SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE

NOTES ON INSTALLING, COOLING-FAN AND CLUTCH

NOTES WHEN APPLYING AN ELECTRIC STARTER, NOTES ON HEATING THE GLOW PLUG

INTRODUCTION, BEFORE STARTING

ENGINE PARTS NAME, INSTALLATION OF THE STANDARD ACCESSORIES

INSTALLATION OF THE ENGINE, FACTS ABOUT GLOWPLUGS

CARBURETOR CONTROLS ABOUT THE PUMP SYSTEM

CARE OF FUEL PUMP AND REGURETOR

ABOUT THE PLUMBING

CONTENTS

2-5

7-8

9-12

13-15

16-17

18-19

21-22

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

CARBURETOR CLEANLINESS ADJUSTMENT CHART

INSTALLATION OF THROTTLE SERVO

CARE AND MAINTENANCE

TROUBLE SHOOTING

ENGINE EXPLODED VIEW & PARTS LIST CARBURETOR EXPLODED VIEW & PARTS LIST

O.S. GENUINE PARTS & ACCESSORIES THREE VIEW DRAWING MEMO

23-25 25-29

30-31

34-37

38-39 40-41

43 44

SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE

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.

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

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These cover events which might involve serious (in extreme circumstances, even fatal) injury.

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Never touch, or allow any object to come into contact with, the rotating parts.

Model engine fuel is poison-

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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.

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 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

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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.

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NOTES

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This engine was designed for model

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helicopters. Do not attempt to use it for any other purpose.

Mount the engine in your model securely, fol-

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lowing the manufacturers' recommendations, using appropriate screws and locknuts.

Install an effective silencer (muffler). Frequent

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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

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each flight. Avoid sudden high r.p.m. immediately after the

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engine is started, as the clutch will engage and you may be struck by the rotor.

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NOTES

After starting the engine, carry out any needle-

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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

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glasses is also strongly recommended. Press the rotor head down securely.

Take care that the glow plug clip or battery

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leads do not come into contact with rotating parts.

Adjust the throttle linkage so that the engine

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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.

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Take care that loose clothing (ties, shirt sleeves,

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scarves etc.) do not come into contact with the rotor. Do not carry loose objects (such as pencils, screwdrivers, etc.) in a shirt pocket from where they could fall through the rotor disc.

For their safety, keep all onlookers (especially

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small children) well back (at least 20 feet or 6 metres) 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

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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.

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NOTES

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 91 (Code No.71530510) 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.

BDC position

Rotate the crankshaft so that the connecting rod comes to this position.

Insert this groove onto the connecting rod.

NOTES WHEN APPLYING AN ELECTRIC STARTER

Because of this 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 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.

Note on heating the glow plug

The heatsink head on the engine is 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 retaining screw.

Example

INTRODUCTION

This is a high performance engine expressly designed for 3D flight with 90 size helicopters basing on the MAX-91SZ-H RING and equipping O.S.'s original PD-07 pump and regulator system. The pump feeds fuel stably irrespective of violent changes in model attitude and the regulator regulates fuel pressure from the pump keeping the pressure at a set level. The 60M-P carburetor with twin needles enables adjustment of idling, hovering and the 'in air flight' independently.

Note:

As delivered, the carburetor is not installed on the engine. Install the carburetor securely on the engine referring to the INSTALLATION OF THE CARBURETOR section.

Standard accessories

Carburetor Complete 60M-P

Carburetor Rubber Gasket

Carburetor Retainer Assembly

(M2.6x18)

Head Gasket

0.2mm

Glow Plug No.8

Woodruff Key Needle Adjusting Screw (M2.6x5 2pcs.)

Instruction manual

0.1mm

BEFORE STARTING

Tools, accessories, etc.The following items are necessary for operating the engine.

Items necessary for starting

Glow Plug

O.S. No.8 is supplied with the engine.

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.

Glowplug battery

The power source for heating the glowplug may be either a large heavy-duty 1.5volt dry cell, Ni-cd battery or glowplug Igniter.

1.5 volt dry cell

Battery leads

glowplug Igniter

In case of 1.5volt dry cell

Make sure glowplug element glows bright red inside room or shadow.

Hexagon starting shaft

This shaft mounted on an electric starting motor is driven into the shaft cup to turn the engine.

Electric starter and starter battery

An electric starter is recommended for starting.

Battery leads

12V Battery

Starter

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 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.

Fuel Pump

Alternatively, one of the purposemade 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 inline filter between the fuel tank and the PD-07 pump to prevent entry of foreign matter into the carburetor.

Silicone Fuel Line

Heatproof silicone tubing of approx. 5mm o.d. and 2.5mm i.d. is required for the connection between the fuel tank and engine.

Manual

Electric

TOOLS

Hex Drivers

Necessary for engine installation.

1.5mm, 2mm, 2.5mm, 3mm

Phillips Screwdriver

No.1, No.2, etc.

Screwdriver

Necessary for carburetor adjustments. No.1, No.2, etc

Socket Drivers

5mm, 5.5mm, 7mm

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

End Wrenches

8mm, 13mm, 14mm, etc.

Needle Nose Pliers

ENGINE PARTS NAME

Heatsink Head

Carburetor Typr 60M-P

Thrust Washer

Crankcase

Propeller nut

Crankshaft

Glowplug

Reguretor

Beam Mount

Throttle Lever

Idle Mixture Control Screw

Mixture Control Valve

Carburetor Rubber Gasket

Cover Plate

Reguretor

Mixture Control Valve Stopper

Medium Speed Needle Valve

Pump Unit (PD-07)

Fuel Inlet

High Speed Needle Valve

Pump Holder

JAPAN

INSTALLATION OF THE STANDARD ACCESSORIES

Insert the carburetor rubber

INSTALLATION OF THE CARBURETOR

Insert the carburetor retainer as illustrated.

1. Unscrew the retainer screw a little.

Carburetor Retainer

Retainer screw

2. gasket on the carburetor body securely. Then, insert the carburetor in the crankcase.

Note: In case it is hard to insert the carburetor in the crankcase, apply oil on the carburetor body. Do not force it, or damage to the carburetor body and/or crankcase can occur.

Rotate the retainer screw gently until it stops, then

3. tighten a further 90-120 degrees. Do not over-tighten the screw as this will damage the carburetor body.

Retainer screw

Carburetor Rubber Gasket

0.2mm gap

INSTALLING THE GLOWPLUG

Install washer on glowplug and insert carefully into Heatsink-head, making sure that it is not cross-threaded before tightening firmly.

Glow plug

Washer

ABOUT THE HEAD GASKET

The engine is installed with a 0.2mm thick head gasket at the factory. If necessary according to the fuel used, atmospheric conditions and glow plug used, adjust the thickness with the extra 0.2mm and

0.1mm gasket supplied with the engine.

ABOUT THE WOODRUFF KEY

Use the woodruff key supplied with the engine if the fan pulley of the model has a groove to accept it.

HEX KEY NEEDLE ADJUSTMENT

The knurled heads of the two needle valves (HighSpeed and Medium Speed) are 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 installed. 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.

Needle Adjusting screw

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

Top surfaces are in the same plane.

Top surfaces are not in the same plane.

Re-align the surfaces as necessary

Make sure that only the undersurfaces of the engine’s mounting lugs are in contact with the engine mount.

CORRECT

INCORRECT

Side view

Top surfaces are not in the same plane.

Engine does not rest firmly.

FACTS ABOUT GLOWPLUGS

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.

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.

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.:

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.

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:

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.

Three adjustable mixture controls are incorporated in the Type 60M-C. They are as follows.

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 60M'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.

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.

Idle MIxture Control Screw

High Speed Needle Valve (Main Needle)

Medium Speed Needle Valve

Needle Adjusting screw

NOTE As the idle mixture control screw is installed with LOCTITE, it may initialy feel 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.

90 degrees

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, 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

Thick

Lean

Mixture Control Valve

GRADUATIONS ON THE CARBURETOR BODY

As shown in the sketch, the carburetor has graduation marks.

Fully opened position

89 degrees

Fully closed position

Carburetor Body

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.

Carburetor Rotor

ABOUT THE PUMP SYSTEM

Fuel passing direction is set in the pump. Do not mistake piping.

Coming in (IN)

Going out (OUT)

(Connect to regulator nipple.)

CARE OF FUEL PUMP AND REGURETOR

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.

DO NOT allow foreign matter to enter the fuel system. Dirt inside the pump or regulator, no matter how small, may obstruct the flow of fuel and prevent these components from working properly.

DO NOT obstruct the small rectangular hole at the bottom of the regulator, nor the regulator will not function correctly.

Rectangular hole

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 allow fuel to remain in the pump. After finishing the day's flight session, be sure to run out the fuel in the pump. Stop the fuel flow to the pump with a stopper and run the engine at idling to use up the fuel in the pump. After stopping the engine, rotate the engine by electric starter to eliminate fuel inside the engine.

ABOUT THE PLUMBING

Follow the procedure shown.

muffler pressure

Fuel tank

Piping 1

Connect silencer pressure nipple to fuel tank after installing the engine and the silencer in the model according to the instructions supplied with the model. Connect fuel tank to 'IN' nipple of the PD-07 pump and 'OUT' nipple of the pump to the regulator nipple. It is recommended to install a good in-line filter between the fuel tank and the PD-07 pump to prevent entry of foreign matter into the carburetor.

Silencer

Fuel Filter (commercially available)

Pump

JAPAN

Fuel Stopper (commercially available)

Piping 2

When an engine r.p.m. control equipment (generally called as Governor) is used, it is expected that the engine runs stably without employing the silencer pressurized system because the engine r.p.m. will not exceed the setting r.p.m. In this case, carry out piping as illustrated. Be sure to use a check valve to prevent the fuel coming out during inverted flight. Also, it is expected to open the needle a little more than Piping 1. In either case, carry out running-in referring to STARTING section.

Silencer

Fuel Filter

Fuel tank

(commercially available)

Check valve (commercially available)

STARTING

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

1. 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:

2. exactly 2 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.

Medium Speed needle-valve:

exactly 1 turn open from the fully closed position.

Open

JAPAN

Pump

Fuel Stopper (commercially available)

Preparation of the starter

3. Install the starting shaft to the starter securely. Improper installation will allow the shaft to swing creating a dangerous situation.

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

6. Without energizing the glowplug, open the throttle a little from the idle position. Turn the engine over using the starter until the fuel is seen to reach carburetor.

Preparation of starting

7. 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.

Starting

8. 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

9. Fully pull down the throttle trim on the transmitter.

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 immediately 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.

RUNNING-IN ("Breaking-in")

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.

ー

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. 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.

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.

Medium-Speed Needle Valve. Turn approximately 30 degrees (3 to 4 click) at a time.

Idle Mixture Control Screw. Turn approximately 5 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.

This carburetor is not equipped with a throttle stop screw. Instead, idle speed is adjusted by means of the throttle trim lever on the transmitter.

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.

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 5 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 5 degrees to enrich the mixture.

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 HighSpeed 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. DO NOT touch the Medium Speed Needle Valve.

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 counterclockwise.

When satisfactory hovering flight has been achieved, land the modeI again and re-check the engine's idle qualities.

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.

Maximum

Adjustment range of Medium Speed Needle Valve

Fuel Flow

Minimum

Fully Closed

1/3

Throttle Opening

Adjustment range of Idle Mixture Control Screw

2/3 Fully Open

Needle Valve too far open

High Speed Needle Valve Setting varies according to the curve.

Needle Valve too far closed

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.

Now adjust the High-Speed Needle Valve to

3. 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.

Having now found the optimum setting for the

4. High-Speed Needle Valve, re-check the engine's idle performance, fine tuning the Idle Mixture Control Screw, if necessary, to perfect the idle.

Now re-check hovering performance It may be

5. 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 kept 1 turn 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.

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 halfturn 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.

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 Photo, right.

Remove this with an 8mm wrench

Dirt and fbrous matter mostly accumulate here

ADJUSTING CHART

High Speed Needle Valve - 2 turns opened from fully closed position. Medium Speed Needle Valve - 1 turns opened from fully closed position.

Observe the mixture condition while "floating" the model

Lean mixture

Turn the Idle Mixture Control Screw counterclockwise 5 degrees

Observe the hovering mixture condition

Lean mixture

Open the High Speed Needle Valve (Turn counter-clockwise)

Turn the Idle Mixture Control Screw counterclockwise 5 degrees

Open the High Speed Needle Valve (Turn counter-clockwise)

Turn the Idle Mixture Control Screw counterclockwise 5 degrees

Open the Medium Speed Needle Valve

Idle for approx: 10 seconds, then reopen throttle to observe transition ("Float" the model)

Lean mixture

Lean mixture Rich mixture

Start the engine

Warm up the engine

Land the model

High Speed Flight

High Speed Flight OK

Fine tuning of idling mixture

Fine tuning of hovering mixture

Adjustment completed

Idling OK

Hovering OK

Idling OK

Hovering OK

Rich mixture

Turn the Idle Mixture Control Screw clockwise 5 degrees

Close the High Speed Needle Valve (Turn clockwise)

Turn the Idle Mixture Control Screw clockwise 5 degrees

Close the High Speed Needle Valve (Turn clockwise)

Turn the Idle Mixture Control Screw clockwise 5 degrees

Close the Medium Speed Needle Valve

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.

Servo output arm

Throttle arm

27mm

Locate the servo so that its output arm and the throttle pushrod are, as close as possible, directry in line with carburetor's throttle arm, as shown.

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 on 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.

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.

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 required, make necessary adjustment at the transmitter.

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.

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

cause the O-rings inside the carburettor to deteriorate.

These procedures will reduce the risk of starting difficulties and of internal corrosion after a period of storage.

TROUBLE SHOOTING

Cause

Fuel tank is empty. Fuel not reaching the engine.

Glowplug element is burnt out. Glowplug battery discharged

Clogged fuel filter

Silencer inside is dirty. Over priming Remove glowplug and pump out excess fuel.

Fill the tank with fuel and repeat Priming procedure.

Replace glowplug.

Recharge or replace the battery.

Clean or replace fuel filter.

Clean inside silencer.

Symptom

Engine fails to fire.

Corrective action

Fuel tubing is disconnected. Fuel tubing is kinked, split or has a hole.

Incorrect carburetor settings

Incorrect servo linkage

Reverse rotating direction of electric starter.

Symptom

Engine fires intermittently but does not run.

Cause

Connect fuel tubing securely. Check the tubing carefully and replace if necessary.

Return the needle valve and mixture control valve to basic position.

Reconnect linkage after setting servo at neutral. Mare sure it rotates counter clockwise seen

from crankshaft side.

Corrective action

Insufficient fuel in the tank. Fill the tank with fuel.

Deteriorated glowplug

Clogged fuel filter

Silencer inside is dirty. Engine overheated

Disconnecting plug battery too soon.

Air bubbles in fuel

Replace glowplug. Clean or replace fuel filter.

Clean inside silencer. Wait until engine has cooled. Do not disconnect plug battery and wait until

r.p.m. become stable. Fit O rings to the tank screws to

prevent bubbles.

Symptom

Unstable idle

Cause

Corrective action

Unsuitable glowplug

Unsuitable fuel

Silencer is disconnected or has play

Symptom

Not reaching expected peak r.p.m.

Cause

Insufficient warming up or running-in. Silencer or manifold is not securely connected

or disconnected. Fuel tubing from tank to is split or broken.

Use suggested glowplug in the instructions.

Do not use extremely high nitro or low oil fuel.

Install silencer securely.

Corrective action

Set the needle only after warming up. Complete running-in.

Check the connections and secure them.

Replace the tubing.

Symptom

Poor response

Cause

Deteriorated glowplug Incorrect carburetor settings

Inaccurate linkage

Symptom

Poor r.p.m. drop

Cause

Too much throttle opening at idle.

Incorrect carburetor fitting

Needle-valve closed too far. Open needle-valve slightly

Replace glowplug. Readjust low r.p.m. range with metering

needle and mixture control valve.

Recheck the throttle opening against the pitch angle.

Lower the throttle trim to adequate position to lower idle r.p.m.

Fit carburetor securely.

Corrective action

ENGINE EXPLODED VIEW

ENGINE PARTS LIST

C.M3x15

C.M2.6x18

2.5x 5.5xL23mm

Type of screw C…Cap Screw M…Oval Fillister-Head Screw

＊

F…Flat Head Screw N…Round Head Screw S…Set Screw

No.

Code No.

29064000

29063100

29503400

29063200

27006000

27917000

29505010

29183010

45010002

46120000

26731002

C.M3x15

C.M3x12

23981700

29061000

27930000

29062000

29061400

29067010

22681953

29067100

72508001

29067110 71608001 27708200 41621100

The specifications are subject to alteration for improvement without notice.

Heatsink Head Cylinder Liner Piston Ring Piston Piston Pin Piston Pin Retainer (2pcs.) Connecting Rod Carburetor Complete 60M-P Propeller Nut



Thrust Washer Crankshaft Ball Bearing (Front) Carburetor Retainer Assembly Crankcase Crankshaft Ball Bearing (Rear) Crankshaft Gasket Set Cover Plate Nipple (No.1) Pump Holder Pump Unit (PD-07) Pump Retaining Screw Assembly Glow Plug No.8 Woodruff Key Needle Adjusting Screw

Description

CARBURETOR EXPLODED VIEW

C.M3x8

1-1

3-3

Type of screw C...Cap Screw M...Oval Fillister-Head Screw F...Flat Head Screw N...Round Head Screw S...Set Screw

10-4

10-3

9-1

C.M2.6x10

8-4

10-2

10-1

3-2

3-1

8-3

8-5

8-2

8-1

CARBURETOR PARTS LIST

No.

1-1

2 3

3-1 3-2 3-3

4 5 6 7 8

8-1 8-2 8-3 8-4 8-5

9-1

Code No.

27381410 22826131 29183210 29181630 27881810 27881800 27881820 45581820 29183100 27881330 27681340 29181900 27981910 24981837 29181940 29181941 26711305 29181980 22681953

Throttle Lever Assembly Throttle Lever Retaining Screw (2pcs.) Carburetor Rotor Mixture Control Valve Assembly "O"Ring (L) (2pcs.)

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

"O"Ring (L) (2pcs.) Rotor Guide Screw Carburetor Body Mixture Control Screw Mixture Control Valve Stopper Needle Valve Assembly Needle "O"Ring (2pcs.) Needle Valve Holder Assembly Needle Valve Holder Ratchet Spring Reguretor Assembly Fuel Inlet

Description

No.

Code No.

27981900

27981910

10-1

24981837

10-2

27381940

10-3

26711305

10-4

29015019

41621100

The specifications are subject to alteration for improvement without notice.

Needle Valve Assembly Needle "O"Ring (2pcs.) Needle Valve Holder Assembly Ratchet Spring Carburetor Rubber Gasket Needle Adjusting Screw (5pcs.)

Description

O.S. GENUINE PARTS & ACCESSORIES

JAPAN

GLOWPLUG

No.8

(71608001)

(71605100)

CRANKSHAFT CLAMP

(For 91SZ-H)

(71530510)

DRIVE HUB ASSEMBLY

(w / woodruff key)

Drive Hub

(27708010)

Woodruff Key

(27708200)

LONG SOCKET WRENCH WITH PLUG GRIP

(71521000)

The specifications are subject to alteration for improvement without notice.

IN-FLIGHT CONTROL NEEDLE VALVE

(71705000)

LOCK WASHER (10set)

(55500003)

SUPER FILTER

(L)

(72403050)

CAP SCREW SET

M3x12

(79871140)

M3x15

(10pcs.)

(79871150)

THREE VIEW DRAWING

SPECIFICATIONS

■

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.

3.3 PS / 15,000 r.p.m. 640g (22.5oz.)

42.5

JAPAN

42.6 61

4- 4.2

) ) )

UNF 5/16-24

88.7

56.4

27.4

87.4

42.8

Dimensions(mm)

MEMO

6-15 3-Chome Imagawa Higashisumiyoshi-ku Osaka 546-0003, Japan

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

TEL. (06) 6702-0225

FAX. (06) 6704-2722

60091750 030600

O.S. Engines 91SZ-H User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual