background image

2

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  or 
abused. 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.

WARNINGS

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

NOTES

These cover the many other possibilities, generally less 
obvious  sources  of  danger,  but  which,  under  certain 
circumstances, may also cause damage or injury.

SAFETY INSTRUCTIONS AND 

WARNINGS ABOUT YOUR 

O.S. ENGINE

WARNINGS

Never  touch,  or  allow  any  object  to  come  into 
contact  with,  the  rotating  propeller  and  do  not 
crouch over the engine when it is running.

A weakened or loose propeller may disintegrate or be thrown 
off and, since propeller tip speeds with powerful engines may 
exceed 600 feet(180 metres) per second, it will be understood 
that such a failure could result in serious injury, (see 'NOTES' 
section relating to propeller safety).

Model engine fuel is 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 an 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.

Never  operate  your  engine  in  an  enclosed  space.  Model 
engines,  like  automobile  engines,  exhaust  deadly  carbon-
monoxide. Run your engine only in an open area.

Model  engines  generate  considerable  heat.  Do 
not  touch  any  part  of  your  engine  until  it  has 
cooled.  Contact  with  the  muffler(silencer), 
cylinder  head  or  exhaust  header  pipe,  in 
particular, may result in a serious burn.

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.

Mount  the  engine  in  your  model  securely,  following  the  manufacturers'  recommendations,  using  appropriate 
screws and locknuts.

Be  sure  to  use  the  silencer  (muffler)  supplied  with  the  engine.  Frequent  exposure  to  an  open  exhaust  may 
eventually impair your hearing. 
Such noise is also likely to cause annoyance to others over a wide area.

Install a top-quality propeller of the diameter and pitch specified for the engine and aircraft. Locate the propeller on 
the shaft so that the curved face of the blades faces forward-i.e. in the direction of flight. Firmly tighten the propeller 
nut, using the correct size wrench.

Always  check  the  tightness  of  the  propeller  nut  and  retighten  it,  if  necessary,  before  restarting  the  engine, 
particularly  in  the  case  of  four-stroke-cycle  engines.  If  a  safety  locknut  assembly  is  provided  with  your  engine, 
always  use  it.  This  will  prevent  the  propeller  from  flying  off  in  the  event  of  a  "backfire",  even  if  it  loosens.  Also, 
check the tightness of all the screws and nuts before restarting the engine.

If you install a spinner, make sure that it is a precision made product and that the slots for the propeller blades 
do not cut into the blade roots and weaken them.

Discard  any  propeller  which  has  become  split,  cracked,  nicked  or  otherwise  rendered  unsafe.  Never  attempt  to 
repair such a propeller: destroy it. Do not modify a propeller in any way, unless you are highly experienced in tuning 
propellers for specialized competition work such as pylon-racing.

Use an electric starter for this engine. The wearing of safety glasses is also strongly recommended.

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 ...

Reviews: