Integrated with O.S. Demand Regulator System 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.
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 • After starting the engine, carry out any needle- This engine was designed for model helicopters. Do not attempt to use it for any other purpose. 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. • Mount the engine in your model securely, fol- lowing the manufacturers' recommendations, using appropriate screws and locknuts. • Use an electric starter.
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. With this engine, the cover plate cannot be removed when the piston is at BDC due to engine construction.
NOTES WHEN APPLYING AN ELECTRIC STARTER Because of the initial tightness, of the piston/sleeve assembly 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.
Note on heating the glow plug Example The heatsink head and the crankcase of on the engine is treated with an anodized finish which does not conduct current. Therefore, when heating the glow plug, connect one lead to the glow plug and the other to the cover plate retaining screw. 10 INTRODUCTION This is the O.S. SPEED version of the 91HZ-R developed expressly for the 3D flights.
ENGINE PARTS NAME Glowplug Heatsink Head Throttle Lever Idle Mixture Control Screw Carburetor Typr 61G Fuel Inlet High Speed Needle Valve Thermo Insulater Mixture Control Valve Stopper Mixture Control Valve Cover Plate Thrust Washer Crankcase Beam Mount Reguretor Medium Speed Needle Valve Carburetor Rubber Gasket Propeller nut Crankshaft 12 BEFORE STARTING Tools, accessories, etc.The following items are necessary for operating the engine. In case of 1.
Fuel Fuel Pump 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.
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.
INSTALLATION OF THE CARBURETOR As delivered, the engine has its carburetor lightly fitted into its intake boss. Secure it as follows. Note: In case it is hard to insert the carburetor in the crankcase, apply oil on the Thermo Insulater. Do not force it, or damage to the Thermo Insulater and/or crankcase can occur. 1. Loosen carburetor retainer screw slightly. 3. Rotate the retainer screw gently until it stops, then tighten a further 90-120 degrees.
ABOUT THE PLUMBING Note: Since the muffler pressurized fuel feed is not used with this engine, plug a nipple on the muffler or replace it with a bolt. Carry out plumbing referring to a sketch on page 21. Connect silicone tubing cut into approx. 10cm to the nipple on the cover plate. Then, connect the check valve supplied with the engine as sketched (Be aware of the direction.) It is suggested to install a stopper as shown in the sketch.
GLOWPLUG Glowplug life Since the glowplug and fuel combination used may have a marked effect on performance and reliability, it would be worthwhile to experiment with different plug types. Recommended O.S. plugs are No.8, No.7 and No.10 (Former A5) . Carefully install plug finger-tight, before final tightening with the correct size plug wrench. Particularly in the case of very high performance engines, glowplugs must be regarded as expendable items.
GRADUATIONS ON THE CARBURETOR BODY BASIC POSITION OF MIXTURE CONTROL SCREW (Mixture Control Valve) As shown in the sketch, the carburetor has graduation marks. 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.
Medium Speed needle-valve: one turn open from the fully closed position. 1. Opening and closing of the Needle-Valve Turn the needle clockwise to close the needlevalve, and turn the needle counter-clockwise to open the needle-valve as shown in the sketch. 3. Preparation of the starter Install the starting shaft to the starter securely. Improper installation will allow the shaft to swing creating a dangerous situation.
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.
ADJUSTMENT Please observe the following before beginning to make any adjustment. 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. High-Speed Needle Valve. Turn this approximately 30 degrees (3 to 4 clicks) at a time, when making initial adjustments; then in steps of approximately 15 degrees (1 to 2 clicks) when making final adjustments.
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 2. 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.
CARBURETOR CLEANLINESS SUBSEQUENT READJUSTMENTS 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.
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.
TROUBLE SHOOTING Symptom Engine fails to fire. Corrective action Cause Fuel tank is empty. Fuel not reaching the engine. Fill the tank with fuel and repeat. Priming procedure. Glowplug element is burnt out. Glowplug battery discharged Replace glowplug. Recharge or replace the battery. Clogged fuel filter. Silencer inside is dirty. Clean or replace fuel filter. Clean inside silencer. Over priming Remove glowplug and pump out excess fuel. Fuel tubing is disconnected.
Symptom Unstable idle Corrective action Cause Unsuitable glowplug Use suggested glowplug in the instructions. Unsuitable fuel Do not use extremely high nitro or low oil fuel. Silencer is disconnected or is loose Install silencer securely. Symptom Not reaching expected peak r.p.m. Corrective action Cause Insufficient warming up or running-in. Set the needle only after warming up. Complete running-in. Silencer or manifold is not securely connected or disconnected.
Heatsink Head Head Gasket (0.1mm) Cylinder Liner Piston Ring Piston Piston Pin Piston Pin Retainer (2pcs.) Connecting Rod Carburetor Complete 61G Propeller Nut Thrust Washer Crankshaft Ball Bearing (Front) Carburetor Retainer Assembly "O" Ring Crankcase Crankshaft Ball Bearing (Rear) Crankshaft Cover Gasket Cover Plate Nipple (No.1) Glow Plug No.8 Check Valve Head Gasket (0.
CARBURETOR EXPLODED VIEW C.M3x8 3 3-1 C.M2.6x7 1-1 10 5 1 10-1 2 4-3 7 6 8 6-1 4-2 4-1 11-4 11-2 12 11-3 9-2 9-3 9-1 9 11-1 11 Type of screw C...Cap Screw 9-4 C.M2x5 4 44 CARBURETOR PARTS LIST No. Code No. 1 1-1 2 3 3-1 4 4-1 4-2 4-3 5 6 6-1 7 8 29085140 79871110 29088250 25881220 79871020 29088320 27881810 27881800 27881820 45581820 29088140 27984900 27881330 27681340 Description Throttle Lever Assembly Retaining Screw (10pcs.
O.S. GENUINE PARTS & ACCESSORIES CRANKSHAFT CLAMP 91 POWERBOOST PIPE 90 GLOWPLUG No.7 Silencer Retaining Screw (29122520) (2pcs.) (71607100) No.8 Exhaust Gasket Set (71608001) (72145020) (2pcs.) No.
MEMO 48 6-15 3-Chome Imagawa Higashisumiyoshi-ku Osaka 546-0003, Japan TEL. (06) 6702-0225 FAX. (06) 6704-2722 C Copyright 2011 by O.S.Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan.
