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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.

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WARNINGS

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.

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.
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 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  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.

Summary of Contents for MAX-25AX & MAX-35AX

Page 1: ...t the same time Two Stroke Engine For Airplanes 1 2 6 7 8 9 10 20 21 22 27 30 33 15 17 SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O S ENGINE ENGINE CONSTRUCTION NOTES WHEN APPLYING AN ELECTTRIC STARTER ABOUT THE ENGINE BASIC ENGINE PARTS BEFORE STARTING INSTALLATION INSTALLATION OF THE STANDARD ACCESSORIES FUEL TANK LOCATION MIXTURE CONTROLS GLOWPLUG STARTING CONTENTS RUNNING IN IDLING ADJUSTMENT...

Page 2: ...sonous 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 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 Model engines generate considerable heat Do not touch any part of your engine until it has cooled C...

Page 3: ...s check the tightness of the propeller nut and retighten it if necessary before restarting the engine 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 Preferably use an electric starter The wearing of safe...

Page 4: ...eparing your model for flight If you have to carry the model to the take off point with the engine running be especially cautious Keep the propeller pointed away from you and walk well clear of spectators Warning Immediately after a glowplug ignition engine has been run and is still warm conditions sometimes exist whereby it is just possible for the engine to abruptly restart if the propeller is c...

Page 5: ...pplied with the engine Needle Valve Extension Cable Set E 3080 Silencer Assembly Silencer Retaining Screw M3x28 2pcs ABOUT THE ENGINE These are high performance two stroke engines designed for sport and aerobatic models Ample power enables to turn a one size larger propeller with lower rpm which results in mild and pleasant exhaust sound The new carburetors needlevalve assembly has now been angled...

Page 6: ... than those shown in the table may be used but remember that the propeller noise will increase due to higher rpm or if a larger diameter lower pitched prop is used Propellers 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 Reminder Warning Make sure that the propeller is well balanced An unbalanced propeller and ...

Page 7: ...oke or allow anyone else to smoke near to it Reminder A fuel tank of approximately 180cc capacity for 35AX and 160cc capacity for 25AX is suggested This allows around 10 minutes flying time dependent upon the type of fuel used the size of propeller and on the amount of full throttle to part throttle operation throughout the flight Fuel Tank 13 S GLOWPLUG IGNITER Commercialy available handy glowplu...

Page 8: ...ible engine mounting for highest performance and safe running Conventional wooden mounting beams should be of rigid hardwood and of at least 12mm or 5 8 in square section Use at least 3mm steel screws such as Allen type with locknuts for bolting the engine to the bearers INSTALLATION CORRECT Top surfaces are in the same plane INCORRECT Front view Side view Re align the surfaces as necessary Opposi...

Page 9: ...hers and locknuts for bolting the engine to the bearers O S Radial Motor Mount A special O S radial motor mount Code No 71908410 is available as an optional extra for use where firewall type mounting is required 17 THROTTLE LINKAGE Before connecting the throttle to its servo make sure that the throttle arm and linkage safely clear any adjacent part of the airframe structure etc as the throttle is ...

Page 10: ...NCER 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 Keep your hands and face away from exhaust gas or you will suffer a burn Reminder The exhaust outlet of the silencer can be rotated to any desired position in the following manner Loo...

Page 11: ...Use a suitable length of best quality 5mm OD x 2 5mm ID silicone tubing for fuel tubing The Fuel line pickup weight should be 10mm away from the back of the tank Position the fuel tank so that approximately 1 3 of the tank height is above the center line of the needlevalve Suggested fuel tank capacity is approx 180cc This will allow 10minute flights 25AX 35AX 21 Attention to tank height Plug comme...

Page 12: ...e and reliability it would be worthwhile to experiment with different plug types Recommended O S plugs are No 8 No 6 Former A3 and No 7 Carefully install plug finger tight before final tightening with the correct size plug wrench GLOWPLUG The role of the glowplug Glowplug life Particularly in the case of very high performance engines glowplugs must be regarded as expendable items However plug life...

Page 13: ...heck the tightness of screws and nuts especially engine mounting and moving parts e g throttle lever 25 Connect battery leads to glowplug Check that the needle valve is closed Do not overtighten Now open the needle valve counter clockwise 2 2 5 turns to the starting setting 3 4 Open the throttle approx one quarter This is to avoid unnecessarily high r p m when the engine starts Turn needle valve c...

Page 14: ...is disconnected close the needle valve to the point where the engine does not stop Run the engine for one minute with the throttle fully open but with the needle valve adjusted for rich slow four cycle operation RUNNING IN Breaking in Now close the needle valve until the engine speeds up to two cycle operation and allow it to run for about 10 seconds then reopen the needle valve to bring the engin...

Page 15: ...essary to arrive at the optimum setting Optimum needle setting 1 Optimum needle setting 2 Slowly advance the throttle to its fully open position then gradually close the needle valve until the exhaust note begins to change 4 cycle to 2 cycle 29 20 45 degrees Needle valve adjustment diagram This diagram is for reference purposes only Actual needle positions may differ from those shown Note Practica...

Page 16: ... about five seconds then open the throttle fully If at this point 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 15 30 degrees If the mixture is excessively rich engine rpm will become unstable opening the throttle will produce a great deal of smoke and rpm may drop suddenly or the ...

Page 17: ...tings except to make minor adjustments to the Needle Valve occasionally to take account of variations in climatic conditions The use of a different fuel however particularly one containing more or less nitromethane and or a different type or proportion of lubricating oil is likely to call for some readjustment of the Needle Valve Remember that as a safety measure it is advisable to increase the Ne...

Page 18: ...tive action 2 3 1 2 3 3 3 3 2 Voltage too high or too low Re check and readjust referring to BEFORE STARTING Continue applying an electric starter If the engine dos not start after more than 4 tries disconnect the current to the glowplug and leave for a few minutes then re energize plug and apply starter If the engine still does not start remove glowplug and pump out excess fuel by applying the st...

Page 19: ...se the needle valve and mixture control valve too far as this will cause a lean setting and over heating of the engine This can in turn create nitromethane oxide leading to internal rusting of the engine Always adjust the needlevalve slightly on the rich side of peak rpm Do not leave unused fuel in the engine at the conclusion of a day s flying Accepted practice is to cut off the fuel supply while...

Page 20: ... 23009006 23108000 22620003 22831000 22511000 22630002 22512000 23107100 23107000 71608001 72200080 23125000 23125540 23125530 22681957 79871280 Cylinder Head Head Gasket Cylinder Piston Assembly Piston Pin Piston Pin Retainer 2pcs Connecting Rod Carburetor Complete Type 21L Propeller Nut Propeller Washer Drive Hub Thrust Washer Crankshaft Ball Bearing F Crankcase Crankshaft Ball Bearing R Cranksh...

Page 21: ...9181620 46066319 22781800 22582100 45581820 22681953 44281970 24981837 26381501 27381940 26711305 22615000 23081706 Description Code No No Throttle Lever Assembly Carburetor Rotor Mixture Control Valve Assembly O Ring L 2pcs O Ring S 2pcs Carburetor Body Roter Guide Screw Fuel Inlet No 1 Needle Assembly O Ring 2pcs Set Screw Needle valve Holder Assembly Ratchet Spring Carburetor Rubber Gasket Carb...

Page 22: ...n Retainer 2pcs Connecting Rod Carburetor Complete Type 21K Propeller Nut Propeller Washer Drive Hub Thrust Washer Crankshaft Ball Bearing F Crankcase Crankshaft Ball Bearing R Crankshaft Cover Gasket Cover Plate Glow Plug No 8 Needle Valve Extension Cable Set E 3080 Silencer Assembly O Ring Assembly Screw Pressure Nipple No 7 Silencer Retaining Screw C M3x28 10pcs No Code No Description 1 2 3 4 5...

Page 23: ...ice Throttle Lever Assembly Carburetor Rotor Mixture Control Valve Assembly O Ring L 2pcs O Ring S 2pcs Carburetor Body Roter Guide Screw Fuel Inlet No 1 Needle Assembly O Ring 2pcs Set Screw Needle valve Holder Assembly Ratchet Spring Carburetor Rubber Gasket Carburetor Retaining Screw 1 2 3 3 1 3 2 4 5 6 7 7 1 7 2 8 8 1 9 10 22081408 23181200 29181620 46066319 22781800 23181100 45581820 22681953...

Page 24: ...0 1 4 28 23024009 1 4 28 L SPINNER NUT LONG PROPELLER NUT SET PROPELLER NUT SET FOR 2C SPINNER 1 4 M5 No 8 71608001 No 6 Fomer A3 71605300 No 7 71607100 47 M3 55500002 The specifications are subject to alteration for improvement without notice LOCK WASHER 10sets M4 55500003 71521000 71531000 71531010 NON BUBBLE WEIGHT NON BUBBLE WEIGHT S 79870030 M3 BLIND NUT 79870040 M4 LONG SOCKET WRENCH WITH PL...

Page 25: ...r output Practical R P M Weight SPECIFICATIONS Dimensions mm 25AX THREE VIEW DRAWING E 3080 Silencer 49 18 30 6 45 25 26 15 19 19 38 33 6 96 2 22 5 53 24 99 5 30 5 61 5 UNF1 4 28 80 5 35 76 8 Displacement Bore Stroke Power output at recommended R P M range Recommended R P M range Power output Practical R P M Weight SPECIFICATIONS Dimensions mm 35AX THREE VIEW DRAWING E 3080 Silencer 5 77 cc 0 352 ...

Page 26: ...50 MEMO C Copyright 2009 by O S Engines Mfg Co Ltd All rights reserved Printed in Japan 60092180 061101 6 15 3 Chome Imagawa Higashisumiyoshi ku Osaka 546 0003 Japan URL http www os engines co jp ...

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