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.
CONTENTS SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE 2-4 INTRODUCTION, INSTALLING THE GLOWPLUG 5 RELOCATION OF CARBURETTOR CONTROLS 6 FUEL TANK, INSTALLATION 7 STARTING 13 RUNNING-IN 13-14 IDLING MIXTURE ADJUSTMENT 15 VALVE ADJUSTING 15-17 CARE AND MAINTENANCE 17-18 O.S.
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. 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.
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.
NOTES • Take care that the glow plug clip or battery leads do not come into contact with the propeller. Also check the linkage to the throttle arm. A disconnected linkage could also foul the propeller. • After starting the engine, carry out any needle-valve readjustments from a safe position behind the rotating propeller. Stop the engine before attempting to make other adjustments to the carburettor.
FS-91S2-P INTRODUCTION The O.S. FS-70S2, FS-91S2 and FS-91S2-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-strokecycle model aircraft engines 40 years later. The FS-91S2-P is fitted with the new O.S. PD-07 diaphragm type fuel pump and matching Type 60N carburettor incorporating a built-in pressure regulator.
RELOCATION OF CARBURETTOR CONTROLS FS-91S2-P As supplied, the FS-70S2, FS-91S2 and FS-91S2-P have their throttle lever on the right hand side and needle-valve control on the left. However, where more convenient for certain installations, these positions may be reversed after rotating the carburettor through 180˚ horizontally. Proceed as follows: 1.
Make sure that these mounting beams are accurately aligned and firmly integrated with the airframe, reinforcing the adjacent structure to absorb vibration. Use 3.5mm or larger steel screws, preferably Allen type hexagon socket head cap screws, with washers and locknuts, for bolting the engine to the bearers. As an alternative to wooden beam mounting, a special O.S. cast aluminium radial motor mount, complete with 3.
EXHAUST HEADER PIPE & SILENCER NEEDLE-VALVE EXTENSION Fit these in the following sequence. Screw the header pipe into the cylinder head until it " bottoms ", then unscrew sufficiently to achieve the desired exhaust angle and tighten the locknut securely with a 14mm wrench. Screw the silencer onto the outer end of the header pipe and tighten the other locknut.
The function of the various tubes connected to the engine and tank (see sketch) are as follows: Make sure there is adequate ventilation. Pipe A: To draw fuel from tank to pump nipple marked 'IN'. Pipe B: To deliver fuel from pump nipple marked 'OUT' to carburettor. Pipe C: To connect crankcase breather nipple (behind camshaft housing) to intake pipe. Pipe D: To deliver crankcase pressure pulses to pump diaphragm.
• NEVER disassemble the fuel pump or pressure regulator. PROPELLERS Their original performance may not be restored after reassembly. The choice of propeller depends on the design and weight of the aircraft and on the type of flying in which you will be engaged. Determine the best size and type after practical experimentation. As a starting point, refer to the props listed in the accompanying table.
When to replace the glowplug GLOWPLUGS Apart from when actually burned out, a plug may need to be replaced because it no longer delivers its best performance, such as when: The FS-70S2, FS-91S2 and FS-91S2-P are supplied with an O.S. Type F glowplug, specially designed for O.S. fourstroke engines. The role of the glowplug With a glowplug engine, ignition is initiated by the application of a 1.5-volt power source.
3. Add the special tapered and slotted locknut and secure with a 12mm wrench while holding the prop nut with the 14mm wrench. Reminders: AII 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. Though not as volatile as gasoline, model engine fuel is also highly inflammable. Keep it away from on open flame, excessive heat, sources of sparks, or anything else that might ignite it.
7. Check these conditions and, instead of pressing the starter button after applying the starter, have the starter spinning before applying it to the engine, to give it a "running start". When the engine starts, slowly open the throttle, leaving the needle-valve at its rich starting setting to promote cool running conditions. However, if the engine slows down because the mixture is excessively rich, the needle-valve may be closed a little to speed it up until it runs evenly.
1. Start and adjust the engine as detailed in the starting instructions. 7. With each successive flight, close the needle-valve very slightly until, at the end of about 10 flights, the needle is set for full power. Do not "over-lean" the mixture in an attempt to extract more power. 2. Now open the throttle fully and run the engine for no more than 5 seconds with the needle-valve tuned to produce near maximum r.p.m.
Realignment of Mixture Control Screw IDLING MIXTURE ADJUSTMENT In the course of making readjustments, it is just possible that the mixture control screw may be inadvertently screwed in or out too far and thereby moved beyond its effective range. The factory setting can be re-established as follows: Set the throttle at the fully closed position. Now carefully rotate the mixture control screw clockwise until it stops.
Note: Valve clearances of all O.S. four-stroke-cycle engines must be checked and reset ONLY WHEN THE ENGINE IS COLD. Procedure is as follows. (2) If a clearance is found to be outside either of these limits, it should be reset as follows. 1. Carefully loosen the locknut on rocker-arm 1/4-1/2 turn with 5mm wrench. (Fig.2.) (1) 1. Remove the cover from the rocker-box on top of the cylinder-head, using the correct size Allen hex key. Locknut Loosen approx. 1/4 to 1/2 turn. Wrench 2.
4. Re-tighten locknut while holding adjusting screw stationary. (Fig.5.) Hold at the screw head. 5. Remove 0.04mm feeler, rotate prop through two revolutions and recheck gap. Fig.5 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.
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 the engine is still running - at full throttle - then, expel as much fuel residue as possible by turning the engine over for 5-10 seconds with the electric starter. Finally, inject some after-run oil through the glowplug hole and turn the engine over several times by hand.
O.S. GENUINE PARTS & ACCESSORIES ■ RADIAL MOTOR MOUNT For FS-70S2(71905000) For FS-91S2/S2-P ■ O.S.GLOW PLUG TYPE F ■ EX EXHAUST HEADER PIPES (71615009) (72109500) (72109600) (71901100) Outside Inside ■ PROPELLER LOCKNUT SET (45910200 For Spinner) ■ BOOSTER CABLE SET (72200110) ■ BOOSTER TERMINAL KIT ■ FLEXIBLE EXHAUST PIPES (72200130) ■ BUBBLESS WEIGHT ■ SUPER FILTER (L) (71531000) (72403050) Code.No.
FS-70S2 EXPLODED VIEW C.M2.6X12 2 C.M3.5X20 3-2 3-1 3 (C.M3.5X15) 4-1 6-4 6-3 6-2 5 1 4 4-2 5-4 5-3 5-2 6 8 6-1 7 5-1 - 20 9 9-1 9-2 = \ q C.M2.6X8 a -2 a -1 w e N.+M3X22 0-2 a -2 s 0-1 0 a h u r y g -1 f t d C.M3.5X8 ] p [ o i p C.M2.
FS-70S2 PARTS LIST No. 1 2 3 3-1 3-2 4 4-1 4-2 5 5-1 5-2 5-3 5-4 6 6-1 6-2 6-3 6-4 7 8 9 9-1 9-2 0 = Code No. 4 5913 000 4 5904 210 4 5961 400 4 5961 410 4 5761 600 4 5361 000 4 5361 100 4 5061 202 4 5960 001 4 5960 100 4 5960 210 4 5960 310 4 5960 400 4 5960 011 4 5960 110 4 5960 210 4 5960 310 4 5960 400 4 4004 110 4 4004 010 4 4068 000 4 4068 100 4 5771 000 4 4082 000 4 4014 010 4 4003 400 Description No. Code No.
FS-91S2 EXPLODED VIEW C.M2.6X12 2 C.M3.5X20 3-2 3-1 3 (C.M3.5X15) 4-1 6-4 6-3 6-2 5 1 6 8 6-1 7 5-1 22 9 4 4-2 5-4 5-3 5-2 9-1 9-2 u - \ = C.M2.6X8 a-2 a-1 q w N.+M3X22 0-2 a-2 s 0-1 0 a h y e t g -1 r d f C.M3.5X8 ] p o i [ p C.M2.
FS-91S2 PARTS LIST No. 1 2 3 3-1 3-2 4 4-1 4-2 5 5-1 5-2 5-3 5-4 6 6-1 6-2 6-3 6-4 7 8 9 9-1 9-2 0 0-1 0-2 = Code No. 4 5913 000 4 5904 210 4 5961 400 4 5961 410 4 5761 600 4 5361 000 4 5361 100 4 5061 202 4 5960 000 4 5960 100 4 5960 200 4 5960 300 4 5960 400 4 5960 010 4 5960 110 4 5960 200 4 5960 300 4 5960 400 4 5904 110 4 5904 010 4 5968 200 4 5968 210 4 5771 000 4 5984 000 4 6115 000 4 5581 700 4 5903 400 4 5903 200 No.
FS-91S2-P EXPLODED VIEW C.M2.6X12 2 C.M3.5X20 3-2 3-1 3 (C.M3.5X15) 4-1 6-4 6-3 6-2 5 1 6 8 5-1 9 4 4-2 5-4 5-3 5-2 9-1 24 9-2 6-1 7 - C.M2.6X8 i a = s -2 s -1 q w N.+M3X22 0-2 s s -2 d 0-1 j 0 u e y h -1 g t f C.M3.5X8 \ [ p o ] [ C.M2.
FS-91S2-P PARTS LIST No. 1 2 3 3-1 3-2 4 4-1 4-2 5 5-1 5-2 5-3 5-4 6 6-1 6-2 6-3 6-4 7 8 9 9-1 9-2 0 0-1 0-2 = No. Code No. q 4 5906 000 w 4 5605 000 e 4 6103 100 r 7 2508 001 t 4 5907 010 y 4 5902 010 u 4 5530 030 i 4 5914 010 o 4 5901 010 p 4 5771 000 [ 4 5231 100 ] 4 5962 010 \ 4 5901 110 a 4 5966 000 s 4 5966 100 s-1 4 5966 110 s-2 2 4881 824 d 4 5564 000 f 2 6731 002 g 4 6120 000 h 4 5908 000 h-1 2 9008 219 j 4 5910 100 4 5925 010 4 5925 100 4 5926 000 7 1615 009 Description Code No.
CARBURETTOR EXPLODED VIEWS & PARTS LIST S.3X3 S.3X3 60R(FS-70S2) 1-3 4 1-2 4 1-2 8 1-5 1-1 1-5 1-1 60P(FS-91S2) 1-3 3 1-4 3 1-4 2 1 2 1 5-2 N.+M3X22 5-2 N.+M3X22 5 5 Code No. 1-2 2 4981 837 1-3 2 6381 501 1-4 2 7381 940 1-5 2 6711 305 2 4 4082 100 3 4 5581 820 4 2 2681 953 5 4 5582 300 5-1 4 6066 319 5-2 2 4881 824 6 7 8 9 4 2 4 4 4082 7881 6115 5581 200 400 000 700 N.+M3X6 6 N.+M3X6 6 ✽ Type of screw 7 1 4 5984 900 1-1 2 4081 970 5-1 9 5-1 9 No.
60N(FS-91S2-P) S.3X3 1-3 1-2 8 2 1-5 1-1 3 1-4 1 5-2 5-1 2-1 N.+M3X22 ✽ Type of screw 4 9 5 No. Code No. 1 2 7681 1-1 2 7681 1-2 2 4981 1-3 2 6381 1-4 2 7381 1-5 2 6711 2 4 5983 2-1 4 5582 3 4 5581 4 2 2681 5 4 5582 5-1 4 6066 5-2 2 4881 6 4 5983 7 8 9 2 7881 4 6115 4 5581 900 970 837 501 940 305 100 400 820 953 300 319 824 200 400 000 700 N.
THREE VIEW DRAWING FS-70S2 Specifications 50 11.50cc/0.702cu.in. 25.8mm/1.016in. 22.0mm/0.866in. 2.000~12.000r.p.m. 1.1bhp/11.000r.p.m. 580g/20.4oz. 55.8 96.4 Displacement Bore Stroke PracticalR.P.M. Output Weight 21 UNF5/16-24 20.3 ■ ■ ■ ■ ■ ■ 66.3 39.6 58 44.
THREE VIEW DRAWING FS-91S2 Specifications ■ ■ ■ ■ ■ ■ Displacement Bore Stroke PracticalR.P.M. Output Weight 14.95cc/0.912cu.in. 27.7mm/1.09in. 24.8mm/0.976in. 2.000~12.000r.p.m. 1.6bhp/11.000r.p.m. 640g/22.6oz.
THREE VIEW DRAWING FS-91S2-P Specifications ■ ■ ■ ■ ■ ■ Displacement Bore Stroke PracticalR.P.M. Output Weight 14.95cc/0.912cu.in. 27.7mm/1.09in. 24.8mm/0.976in. 2.000~12.000r.p.m. 1.6bhp/11.000r.p.m. 650g/23.0oz.
Q U A LIT Y PRECISION & P ERFO RM AN NC E UN ES LED CE UAL EQ T AB L IS H IN G T H E STA N D A R D S O F EXCE LLE 6-15 3-Chome Imagawa Higashisumiyoshi-ku Osaka 546-0003, Japan TEL. (06) 6702-0225 FAX. (06) 6704-2722 C Copyright 2000 by O.S.Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan. URL : http://www.os-engines.co.
