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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  2-4  of  this  booklet  and  to 
strictly adhere to the advice contained therein.

Also, please study the entire contents of this 
instruction  manual,  so  as  to  familiarize 
yourself with the controls and other features of 
the engine.
Keep these instructions in a safe place so that 
you  may  readily  refer  to  them  whenever 
necessary.
It is suggested that any instructions supplied 
with the aircraft, radio control equipment, etc., 
are accessible for checking at the same time.

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2-4

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9-10

11-12

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15-17

17-18

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20-25

26-27

28-30

 

13-14

SAFETY INSTRUCTIONS AND 
WARNINGS ABOUT YOUR O.S. ENGINE

INTRODUCTION, INSTALLING THE GLOWPLUG

RELOCATION OF CARBURETTOR CONTROLS

FUEL TANK, INSTALLATION

EXHAUST HEADER PIPE AND SILENCER,
THROTTLE LINKAGE, 
NEEDLE-VALVE EXTENSION

FUEL LINES

CARE OF FUEL PUMP AND REGULATOR,
PROPELLERS

GLOWPLUGS, FUEL

PROPELLER AND SPINNER ATTACHMENT,
TYPE 60R, 60P AND 60N CARBURETTOR

CONTENTS

RUNNING-IN

IDLE MIXTURE ADJUSTMENT

VALVE  ADJUSTING

CARE AND MAINTENANCE

O.S. GENUINE PARTS & ACCESSORIES

ENGINE EXPLODED VIEWS &
ENGINE PARTS LISTS

CARBURETTOR EXPLODED VIEWS &
PARTS LIST

ENGINE THREE VIEW DRAWINGS

STARTING

13

Summary of Contents for 91sII

Page 1: ...control equipment etc are accessible for checking at the same time 1 2 4 5 6 7 8 8 9 9 10 11 12 12 15 15 17 17 18 19 20 25 26 27 28 30 13 14 SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O S ENGINE INTRODUCTION INSTALLING THE GLOWPLUG RELOCATION OF CARBURETTOR CONTROLS FUEL TANK INSTALLATION EXHAUST HEADER PIPE AND SILENCER THROTTLE LINKAGE NEEDLE VALVE EXTENSION FUEL LINES CARE OF FUEL PUMP AND REG...

Page 2: ...ny 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 The advice which follows is grouped under two headings according to the degree of damage or danger which might arise through misuse or neglect 3 NOTES This engine was designed for model aircraft Do not attempt to use it for any other purpose M...

Page 3: ...y flipped over compression WITHOUT the glowplug battery being reconnected Remember this if you wish to avoid the risk of a painfully rapped knuckle NOTES 5 The O S FS 70SⅡ FS 91SⅡ and FS 91SⅡ P are built like all O S engines to the highest engineering standards by a company that was established in 1936 to manufacture 2 stroke engines and which pioneered the production of four stroke cycle model ai...

Page 4: ...p to 12 13 minutes flying time dependent upon the type of fuel used the size of the propeller and on the proportion of full throttle to part throttle operation through the flight Make sure that the tank is well rinsed out with methanol or glow fuel before installation and that the pickup weight is well clear of the bottom of the tank when held vertically see sketch To prevent the pickup from adher...

Page 5: ... with the header pipe or silencer may result in a serious burn If you need to tighten the silencer joints which may loosen when they are hot use a thick folded cloth for protection FUEL LINES For fuel line use heavy duty silicone rubber tubing of approximately 2 5mm inside and 5 0mm outside diameter Note Be sure to use a muffler pressurized fuel feed system It is advisable to fasten connections wi...

Page 6: ...ted on a methanol based fuel containing not less than 18 castor oil or a top quality synthetic lubricant or a mixture of both plus a small percentage 5 15 of nitromethane for improved flexibility and power The carburettor is adjusted at the factory for a fuel containing 20 lubricant and 10 nitromethane Some commercial fuels also contain coloring additives as an aid to fuel level visibility In some...

Page 7: ...ylinder automatically Starting procedure is as follows Check that the current to the glowplug is switched off Check that the polarity of the starter battery leads rotates the engine counter clockwise when viewed from the front Open the needle valve 3 3 5 turns from the fully closed position and temporarily set the throttle in the fully open position Apply the starter and press the starter switch f...

Page 8: ...y cause the engine to stall Therefore at this time the aircraft should as far as is possible be flown at an altitude sufficient to enable an emergency landing to be safely made if the engine stops 9 15 Feeler gauge 0 04mm ALL O S four stroke engines have their valve tappet clearances correctly set before they leave the factory However if after many hours of running time have been logged a loss of ...

Page 9: ...te prop through two revolutions and recheck gap 5 If clearance is correct loosen the locknut on the other rocker arm and repeat steps 1 to 5 above Finally replace rocker box cover 6 Remember Excessive valve clearance will cause loss of power due to valve s not opening sufficiently On the other hand a total loss of clearance may cause difficult starting due to valves not closing properly resulting ...

Page 10: ...g must be cleansed separately in methanol or glow fuel On no account must they come into contact with kerosene Before completely reassembling the engine make sure that no kerosene remains inside that could find its way into the pump unit carburettor etc Inject sparingly preserving oils rust inhibitors etc unless approved for silicone rubber products An appropriate alternative here may be one of th...

Page 11: ...925010 45910100 44014010 44001100 Cam Cover Camshaft Camshaft Ball Bearing 1pc Breather Nipple No 5 Crankcase Crankshaft Ball Bearing R Crankshaft Cover Plate Cylinder Liner Connecting Rod Piston Pin Piston Piston Ring Carburetor Complete Type 60R Breather Nipple No 5 Intake Pipe Intake Pipe Assembly Cylinder Head w valve Assembly Cylinder Head w Gasket Split Cotter 2pc 1pair Valve Spring Retainer...

Page 12: ...00 45925010 45910100 45903200 Description Code No No The specifications are subject to alteration for improvement without notice Description Code No No Cam Cover Camshaft Camshaft Ball Bearing 1pc Breather Nipple No 5 Crankcase Crankshaft Ball Bearing R Crankshaft Cover Plate Cylinder Liner Connecting Rod Piston Pin Piston Piston Ring Carburetor Complete Type 60P Breather Nipple No 5 Intake Pipe I...

Page 13: ... 45231100 45771000 45901010 45914010 45530030 45902010 45907010 72508001 46103100 45605000 45906000 71615009 45926000 45925100 45925010 45910100 Cam Cover Camshaft Camshaft Ball Bearing 1pc Breather Nipple No 5 Crankcase Crankshaft Ball Bearing R Crankshaft Cover Plate Cylinder Liner Connecting Rod Piston Pin Piston Piston Ring Carburetor Complete Type 60N Breather Nipple No 5 Intake Pipe Intake P...

Page 14: ...4081970 45984900 1 1 1 1 2 1 3 1 4 1 5 2 3 4 5 5 1 5 2 6 7 8 9 Description Code No No Needle Valve Assembly Needle Assembly O Ring 2pcs Set Screw Needle Valve Holder Assembly Ratchet Spring Carburetor Body Rotor Guide Screw Fuel Inlet No 1 Mixture Control Valve Assembly O Ring L 2pcs O Ring S 2pcs Carburetor Rotor Throttle Lever Assembly Carburetor Rubber Gasket Carburetor Retaining Screw 2pcs 27 ...

Page 15: ... Stroke PracticalR P M Output Weight Specifications THREE VIEW DRAWING C Copyright 2000 by O S Engines Mfg Co Ltd All rights reserved Printed in Japan TEL 06 6702 0225 FAX 06 6704 2722 6 15 3 Chome Imagawa Higashisumiyoshi ku Osaka 546 0003 Japan 60090990 061107 URL http www os engines co jp U N E Q U A LLED QUALITY PRECISION PERFOR M A N C E E S T A BLISHING THE STANDARDS OF EXCELLE N C E ...

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