Two-Stroke Engine For Airplanes It is of vital importance, before attempting to operate your engine, to read the general 'SAFETY INSTRUCTIONS AND WARNINGS' section on pages 2-6 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.
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.
NOTES This engine was designed for model aircraft. Do not attempt to use it for any other purpose. If you remove the glowplug from the engine and check its condition by connecting the battery leads to it, do not hold the plug with bare fingers.Use an appropriate tool or a folded piece of cloth. Mount the engine in your model securely, following the manufacturers' recommendations, using appropriate screws and locknuts.
NOTES 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. 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.
NOTES WHEN APPLYING AN ELECTRIC 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. 8 ABOUT THE ENGINE This manual handles 35AX. MAX-25AX & MAX- 25AX/35AX STANDARD ACCESSORIES Glow Plug No.
BASIC ENGINE PARTS Glowplug Cylinder head Carburetor Type 21K (Type 21L For 25AX) Cover Plate Propeller washer Propeller nut Beam Mount Crankshaft Crankcase Drive Hub MAX-35AX is shown. 10 BEFORE STARTING Warning: Make sure that the propeller is well balanced. An unbalanced propeller and/or spinner can cause serious vibration which may weaken parts of the airframe or affect the safety of the radio-controlled system.
FUEL 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. The 25AX and 35AX should be operated on a methanol based fuel containing not less than 18% (volumetric) castor oil, or a top quality synthetic lubricant (or a mixture of both), plus a small percentage (5-20%) of nitromethane for improved flexibility and power.
LONG SOCKET WRENCH WITH PLUG GRIP TOOLS Recommended for easy removal and replacement of the angled and recessed glowplug, the O.S.Long Socket Wrench incorporates a special grip. HEX Screwdriver Necessary for engine installation. 1.5mm, 2.5mm 8mm Phillips Screwdriver No.2, etc. End Wrenches 10mm, etc. SCREWDRIVER Necessary for mixture control valve adjustments. 14 INSTALLATION It is suggested to use as heavy and rigid as possible engine mounting for highest performance and safe running.
How to fasten the mounting screws. ● Hardwood mounting beams 3mm steel nuts Spring washer or lock washer Tighten second nut firmlydown onto first nut. Tighten this nut first. 12mm min. 12mm min. Hardwood such as cherry or maple. Steel washer 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. 3mm steel screw Radial motor mount (cast aluminum) 3.
INSTALLATION OF THE STANDARD ACCESSORIES NEEDLE-VALVE EXTENSION The needle-valve supplied with this engine is designed to incorporate an extension so that, when the engine is enclosed within the fuselage, the needle-valve may be adjusted from the outside. For this purpose a Needle Valve Extension Cable Set is supplied with the engine.
FUEL TANK LOCATION 25AX Suggested fuel tank capacity is approx 160cc. This will allow 10-12 minute flights. Position the fuel tank so that approximately 1/3 of the tank height is above the center line of the needlevalve. 35AX Suggested fuel tank capacity is approx 180cc. This will allow 10minute flights. Be sure to use a pressurized fuel system by connecting the muffler pressure nipple to the vent-pipe of the fuel tank.
MIXTURE CONTROLS Two mixture controls are provided on the Carburetor. Needle Valve The Needle Valve When set to produce maximum power at full throttle, this establishes the basic fuel/air mixture strength. The correct mixture is then maintained by the carburetor's built-in automatic mixture control system to cover the engine's requirements at reduced throttle settings. Mixture Control Valve Mixture Control Valve on the carburetor is set at basic position ( a little on the rich side) at the factory.
STARTING Be sure to use an electric starter to start the engine. ! Element glows when energized. Pliers Never fail to check the tightness of screws and nuts, especially engine mounting and moving parts (e.g. throttle lever). Replace the plug when the element does not glow or is burnt out. Starting procedure is as follows: 1. Fill the fuel tank with fuel. When filled, prevent the fuel from flowing into the carburetor with a commercially available fuel stopper, etc.
Attention : Do not choke the carburetor air intake when applying the starter. This could cause an excessive amount of fuel to be drawn into the cylinder which may initiate a hydraulic lock and damage the engine. If the engine does not start within 10 repeat applications of the starter, remove the glowplug, check that it glows brightly and that the cylinder is not flooded with fuel. (To eject excess fuel, close needle-valve and apply starter with glowplug removed.) Then try again.
Optimum needle setting(1) Slowly advance the throttle to its fully open position, then gradually close the needle-valve until the exhaust note begins to change. (4cycle to 2-cycle) 4. During subsequent flights, the needle-valve can be gradually closed to give more power. However, if the engine shows signs of running too lean, the next flight should be set richer. After a total of ten flights, the engine should run continuously, on its optimum needle-valve setting, without loss of power as it warms up.
Yes. Refer to the next section. OK Does the engine regain full power immediately? Engine stops. No. Apply full throttle. Does the engine stop? Engine stops. Run at idle speed for 5 seconds. Close the throttle. Yes. Does the engine regain full power? Engine stops. Open the throttle fully. Re-set the idle speed at a little higher r.p.m. Continue running at high speed for 10 seconds.
REALIGNMENT OF MIXTURE CONTROL VALVE In the course of making carburetor adjustments, it is just possible that the Mixture Control Valve may be inadvertently screwed in or out too far and thereby moved beyond its effective adjustment range. The basic position can be found in the sketch shown below. SUBSEQUENT STARTING PROCEDURE Once the optimum needle-valve setting has been established (see page 29, Needle-valve adjustment diagram) the procedure for starting may be simplified as follows. 1.
TROUBLE SHOOTING WHEN THE ENGINE FAILS TO START Four key points For quick, reliable starting, the following four conditions are required. 1 Good compression. 2 Adequate "glow" at glowplug. 3 Correct mixture. 4 Sufficient electric starter rotating speed. If the engine fails to start, or does not keep running after being started, check symptoms against the following chart and take necessary corrective action.
CARE AND MAINTENANCE Please pay attention to the matters described below to ensure that your engine serves you well in regard to performance, reliability and long life. Install an in-line fuel filter between the tank and carburetor to prevent foreign matter in the tank from entering the carburetor. Clean these filters periodically.
39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Description 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) 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.
L CARBURETOR EXPLODED VIEW N.+M3x6 3 3-1 1 3-2 2 5 4 6 S.M3X3 N.+M3.5x5 8-1 9 7-2 7-1 8 7 10 Type of screw N...Round Head Screw S...Set Screw 40 21L CARBURETOR PARTS LIST No. Code No. 1 2 3 3-1 3-2 4 5 6 7 7-1 7-2 8 8-1 9 10 22081408 22582200 29181620 46066319 22781800 22582100 45581820 22681953 44281970 24981837 26381501 27381940 26711305 22615000 23081706 Description Throttle Lever Assembly Carburetor Rotor Mixture Control Valve Assembly "O" Ring (L) (2pcs.) "O" Ring (S) (2pcs.
43 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Description Cylinder Head Head Gasket Cylinder & Piston Assembly Piston Pin Piston Pin 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.
21K CARBURETOR EXPLODED VIEW N.+M3x6 3 3-1 1 3-2 2 5 4 6 S.M3X3 N.+M3.5x5 8-1 9 7-2 7-1 8 7 10 Type of screw N...Round Head Screw S...Set Screw 44 21K CARBURETOR PARTS LIST No. Code No. 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 44281970 24981837 26381501 27381940 26711305 22615000 23081706 Description Throttle Lever Assembly Carburetor Rotor Mixture Control Valve Assembly "O" Ring (L) (2pcs.) "O" Ring (S) (2pcs.
O.S. GENUINE PARTS & ACCESSORIES O.S.GLOW PLUG No.6 (Fomer A3) RADIAL MOTOR MOUNT SPINNER NUT (71908410) 1/4"-28 (23024008) (71605300) 1/4"-28(L) (23024009) No.7 (71607100) LONG PROPELLER NUT SET 1/4"-28 (73101000) No.8 (71608001) PROPELLER NUT SET FOR 2C SPINNER SILENCER EXTENSION ADAPTORS 1/4"-M5 (73101020) (22625103) Width 12.5mm SUPER FILTER (L) (72403050) Screw hole pitch 35.
AX THREE VIEW DRAWING 96.2 SPECIFICATIONS Displacement Bore Stroke Power output at recommended R.P.M. range Recommended R.P.M. range Power output Practical R.P.M. Weight 80.5 4.07 cc / 0.248 cu.in. 18.0 mm / 0.709 in. 16.0 mm / 0.630 in. 0.7 ps / 14,000 r.p.m. 33.6 38 19 (E-3080 Silencer) 19 2,500-15,000 r.p.m. 0.8 ps / 16,000 r.p.m. 2,500-17,000 r.p.m. 275 g / 9.70 oz. 83.0 g / 2.93 oz 15 76.8 35 UNF1/4-28 24 30.6 45 30.5 25 26 59.2 18 22.5 53 99.
MEMO 50 URL : http://www.os-engines.co.jp 6-15 3-Chome Imagawa Higashisumiyoshi-ku Osaka 546-0003, Japan C Copyright 2009 by O.S.Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan.
