O S SPEED R21GT II High-Performance GT Engine Instruction Manual

O S SPEED R21GT II High-Performance GT Engine

Product Information

The product is an engine that requires adjustment and maintenance for optimal performance. It has a carburetor that needs adjustment after the running-in period, a needle valve, and a metering needle for fuel control. It is important to set the throttle at the correct position before starting the engine to avoid overheating and damage. Regular cleaning of filters and the carburetor is necessary, and it is recommended to drain out any remaining fuel and use after-run oil to reduce starting difficulties and corrosion after storage. Dirt and dust should be removed promptly, and necessary parts should be replaced if the engine does not develop normal performance after long-term use. Genuine parts and accessories are also available for purchase.

Product Usage Instructions

1. After the running-in period, adjust the needle valve and metering needle for optimal fuel control. Refer to the instruction manual for standard positions, but keep in mind that positions may vary depending on the fuel and silencer used.
2. Before starting the engine, set the throttleint the correct position to avoid overheating and damage. Do not allow the engine to run with the throttle too far open under “no load” conditions.
3. Clean the filters and carburetor regularly to remove dirt and lint that accumulate on the filter screens.
4. After each operating session, drain out any remaining fuel from the fuel tank. Energize the glow plug and try to restart the engine to burn off any remaining fuel inside the engine. Repeat this procedure until the engine fails to fire. Inject after-run oil into the engine and rotate it with an electric starter for 4 to 5 seconds to distribute the oil to all working parts. Do not inject after-run oil into the carburetor.
5. When cleaning the exterior of the engine, use methanol or a household cleaning agent. Do not use gasoline, kerosene, or any petroleum-based chemical that can damage silicone fuel tubing. Promptly remove dirt and dust from marked places.
6. When storing the engine, install dust caps on the exhaust port, carburetor, etc. to prevent dust from entering the engine.
7. If the engine does not develop normal performance after long-term use, check for worn parts such as ball bearings, cylinder & piston assembly, connecting rod, and/or crankcase. Replace necessary parts.
8. Genuine parts and accessories are available for purchase, including T series plugs, carburetor reducers with O-rings and aluminum, and more.

SAFETY INSTRUCTIONS

SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR o.s. ENGINE
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 an 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.

• 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 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.

WARNINGS!

• Model engine fuel is poisonous. Do not allow it to come into contact with the eyes or mouth? Always store it in a marked container and out of the reach of children.
• 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 it.
• 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 operate your engine in an enclosed space. Model engines, like automobile engines, exhaust deadly carbon monoxide. Run your engine only in an open area.

NOTES

• This engine is intended for model cars. 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.
• Install an effective silencer (muffler). Frequent close exposure to a noisy exhaust (especially in the case of the more powerful highspeed engines) may eventually impair your hearing and such noise is also likely to annoy others over a wide area.
• The wearing of safety glasses is also strongly recommended.
• Take care that the glowplug clip or battery leads do not come into contact with rotating parts. Also ,check that the linkage to the throttle arm is secure.
• For their safety, keep all onlookers (especially small children) well back (at least 20 feet or 6 meters) when preparing your model for running.
• Before starting the engine, always check the tightness of all the screws and nuts especially those of joint and movable parts such as throttle arm. Missing retightening of the loose screws and nuts often causes the parts breakage that is capable of harming you.
• To stop the engine, fully retard the throttle stick and trim lever on the trans-miller, or, in an emergency, cut off the fuel supply by pinching the fuel delivery line from the tank.
• 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 it is rotated over compression WITHOUT the glowplug battery being reconnected.

ENGINE CONSTRUCTION
With this engine, the piston will feel tight at the top of its stroke (TDC) when the engine is cold. This is normal. The cylinder bore has a slight taper. The piston and cylinder are designed to achieve a perfect running clearance when they reach operating temperature.

NOTES WHEN APPLYING AN ELECTRIC STARTER
Do not over-prime. This could cause a hydraulic lock and damage the engine on the application of the electric starter. If over-primed, remove gthe lowplug, close needle valve and apply sthe tarter to pump out surplus fuel. Cover the head with a rag to prevent any pumped-out fuel from getting into your eyes.

NOTES ON OPERATION

ABOUT THE WARRANTY
Since this is a special SPEED version, individual special parts are available only for a limited period (one year after finishing the production). Also, the engine is free of warranty due to damage and/or wear that occurred during running.

While Operating

• Please do not run on a public street, this could cause serious accidents, personal injuries, and/or property damage.
• Please do not run near pedestrians or small children.
• Please do not run in small or confined areas.
• Please do not run where loud noises can disturb others, such as hospitals and residential areas.

NOTE As delivered, the engine has the carburetor lightly fit into its intake. Secure it by changing its angle according to the car chassis.

ABOUT THE ENGINE
O.S.SPEED R21GT II is a factory-tuned engine designed for 1/8 GT touring car competitions. While inheriting the smooth feel and good fuel efficiency of the previous model 0.S.SPEED R21GT, the power feeling in the medium and low-speed range has been improved by a re-designed counterbalance made of tungsten on the crankshaft. The newly designed inner head improves idling stability, and an 0-ring is used to reduce vibration and improve dust resistance. OThe outerhead has been reduced in weight to have better corner balance.

ACCESSORIES

Standard accessories

• T Series Plug RP6 (Turbo head) 1pc.
• Carburetor Reducer (Red) 07 1pc. (w/ “0” Ring)
• Exhaust Seal Ring 1 pc.
• Dust Cap Set 03,016,018 1 pc. each
• Instruction Manual

COMBO SET (With the above accessories)

• TB01 EFRA2042 (T-2060SC WN) Tuned Silencer
  • Joint Spring (3pcs.)
  • Exhaust Seal Ring (1 pc.)
• MB01-70 (M2003SC) Exhaust Header Pipe
  • Exhaust Header Pipe Spring 102mm (2 pcs.)
  • Exhaust Seal Ring (1 pc.)

TOOLS, ACCESSORIES, etc.
The following items are necessary for operating the engine. Items necessary for starting

• FUEL
  Generally, it is suggested that the user selects a fuel that is commercially available for model two-stroke engines. When the brand of fuel is changed, or the nitro content increases, it is advisable to repeat the running-in procedure referred to in the RUNNING-IN paragraphs. Please note that with high-nitro fuels, although power may be increased for competition purposes, glowplug elements do not last as long and engine life will be shortened.

• FUEL FILTER
  To be installed in the fuel line between fuel tank and carburetor to prevent foreign matter from entering the carburetor.

• GLOWPLUG IGNITER
  Commercially available handy glowplug heater in which the glowplug battery and battery leads are integrated.

• STARTER BOX
  For starting the engine.

• FUEL PUMP
  For filling the fuel tank, a simple, polyethylene “squeeze” bottle, with a suitable spout, is required.

• 0.S. SPEED SILICONE FUEL LINE (optional extra)
  The connection between the fuel tank and the engine. 2.5mm ID

• 0.S. SPEED TOOLS (optional extra)

BASIC ENGINE PARTS

INSTALLATION OF THE STANDARD ACCESSORIES

Installing the glow plug. Insert RP6 plug supplied into heatsink head carefully, making sure that it is not cross-threaded before tightening firmly. (All the 0.S. T-Type plugs including the RP6 are not supplied with a washer.) Install the exhaust seal ring supplied.

Use the standard accessory, 7mm reducer in the carburetor.

CARBURETOR CONTROLS• STANDARD POSITIONS (POSITIONS WHEN THE ENGINE LEAVES THE FACTORY)
Four adjustable controls are provided on this carburetor.

• The Needle-Valve:
  For adjusting air/fuel ratio (air-fuel mixture) at maximum rpm (fully opened throttle).

• The Mixture Control Valve:
  For adjusting acceleration feeling. (Adjusting range should be within ±1 turn.)

• The Metering Needle:
  For adjusting idle and acceleration feelings.

• The Throttle Stop Screw:
  For setting the minimum idle speed:

NOTE: While the Mixture Control Valve and the Metering Valve are set at the standard position when the engine leaves the factory, readjustment may be necessary, occasionally to allow for changes in fuel formula and climatic conditions Readjust the controls only when satisfactory results cannot be obtained with the standard positions following the instructions mentioned in the “CARBURETOR ADJUSTMENT” section.

INSTALLATION OF THE CARBURETOR
As delivered, the engine has its carburetor lightly installed in the intake boss. Secure it as follows.

1. Loosen the retainer screw, rotate the carburetor to its correct position and make sure that it is pressed well down into the intake boss, compressing the rubber gasket, before retightening screw.
2. Rotate the retainer screw gently until it stops, then tighten a further 120-180. Do not overtighten the screw as this will damage the thermo insulator.

Note
Be careful not to damage the O rings when removing the carburetor retainer from the engine. First, remove the retainer Retaining screw, then pull out each part. Do not push the part in or damage the O rings.

ENGINE INSTALLATION
Make sure that the vehicle’s engine mounting surfaces are level and in the same plane. Poor installation may cause distortion of the crankcase, bearings, etc., resulting in erratic running and loss of performance. The recommended screws for securing the engine are 3mm or 4-40 steel Allen hexagon socket type. If existing holes in the engine mount do not align perfectly with engine mounting lugs, enlarge them slightly with a needle file so that screws are in alignment with the mounting holes.

NOTE The engine bottom may interfere with chassis of some models. In this case, file off the chassis so that the engine may not interfere with the chassis when it is installed.

INSTALLING THE MANIFOLD AND SILENCER TO THE ENGINE
Install Exhaust Seal Ring to the silencer. Secure the manifold and silencer with Silencer Joint Springs. After that, fit the manifold into the exhaust of the engine and secure with the Exhaust Header Pipe Springs.

STARTING THE ENGINE & RUNNING-IN (‘Breaking-in)
Running-in is a procedure for an engine to come close to actual running conditions (fuel, r.p.m., engine temperature, etc.). Excessively rich running and prolonged low-speed running should be avoided. Prolonged low-speed running and low-temperature running may result in the oil in the fuel becoming gelled and the piston/liner becoming stuck together.

PRESSURIZED FUEL SYSTEM

• It is recommended that a muffler pressurized fuel feed system be used so that the fuel may be stably fed to the carburetor.

The following procedure is suitable when a fuel containing 25% nitro- methane is used.

1. Set the carburetor controls at the standard positions (positions when the engine leaves the factory.)
2. Switch the transmitter and make sure that each linkage moves correctly.
3. Make sure rotating direction of the starter box is correct (counter-clockwise seen from the front edge of the crankshaft), and turn the engine with the starter box to draw fuel into the engine.
4. Connect a glowplug ignitor to heat the plug and start the engine with the starter box. When the engine does not start or stops right after being started, try the followings.
   • Close the needle-valve approx. 90° from the standard position.
   • Set the throttle opening a little wider (approx. 1 mm) than the standard selling by adjusting the Throttle Stop Screw.
5. When the engine starts, warm it up by repeatedly increasing the rpm to medium speed and back again to a fast idle with the mixture set very rich, glowplug connected, and the driving wheels clear of the ground. The rich mixture will provide adequate lubrication and cooling, indicated by profuse exhaust smoke.
6. Remove the glowplug ignitor when the engine is warmed up and continue running in on a starter box around 2-3 tanks with full-throttle. Remain the carburetor setting very rich as long as the engine does not go into stall.
7. When the engine is warmed up, disconnect the glowplug battery and try running the car on the track. If the engine stops soon after running at around mid speed, the mixture is too rich. Close the needle valve 15~30°. If the engine still stalls, close the metering needle 15~30°. Run the car on the track until one tank of fuel has been consumed, then close the needle valve very little (within 10°).
8. Repeat this procedure (close needle-valve very little after one tank of fuel has been consumed) until approx. 2 liters of fuel have been consumed, extending gradually the full throttle running time at the straight. Carefully observe the exhaust smoke. Be sure to run the engine with visible white smoke at all times. If the smoke is not visible, the needle valve is closed too far.

Note: In the event of any major working parts (e.g. piston/cylinder liner assembly) being replaced or the fuel being changed, especially to high nitro fuel, the complete running-in should be repeated.

How to stop the engine
To stop the engine, close the throttle to idle speed and shut it off completely with the trim lever on the transmitter then cut off the fuel supply by pinching the fuel delivery tube to the carburetor.

Warning!
Do not touch rotating parts, engine and silencer when stopping the engine as they become very hot, and contact with them may result in a serious burn.

CARBURETOR ADJUSTMENT
Carburetor adjustment should be carried out only after the running-in has been completed.

1. NEEDLE VALVE ADJUSTMENT
   Run the vehicle (with throttle fully open) over the longest available straight course a few times to observe the model’s speed. Return the vehicle to the starting point and close the Needle-valve 15°and repeat the run, taking note of the improvement in performance. Continue with further runs, gradually reduce the Needle-valve setting aiming to achieve the highest straight-line speed (optimum position). Remember, however, if the Needle-valve is closed too far, the engine will overheat, accompanied by visibly diminished exhaust smoke and the model will lose speed. At this point, throttle down immediately, stop the vehicle and reopen the Needle-valve 30~45°.

2. METERING NEEDLE ADJUSTMENT
   After setting the Needle-valve at optimum position, run the vehicle a few times at the straight line. With the engine running, close the throttle and allow it idle for about five seconds, then reopen the throttle fully. If, at this point, the engine puffs out an excessive amount of smoke and the vehicle does not accelerate smoothly and rapidly or even stops, it is probable that the idle mixture is too rich. In this case, turn the Metering needle clockwise 15~30°. If, on the other hand, the engine tends to speed up momentarily and then cut out abruptly when the throttle is opened, the idle mixture is too lean. In this case, turn the Metering needle counter-clockwise 15~30°.

3. THROTTLE STOP SCREW ADJUSTMENT
   If the engine runs too fast with the throttle closed, the throttle stop screw should be turned counter-clockwise to allow the throttle opening to be reduced.

OPTIMUM MIXTURE CONTROL POSITION

With the optimum mixture control position, light smoke is visible during high- speed running and the engine rpm increases smoothly during acceleration. Carry out adjustment 1.~3. patiently until the engine responds quickly and positively to the throttle control. Remember that, if the engine is operated with the fuel/air mixture slightly too lean, it will overheat and run unevenly. As with all engines, it is advisable to set both the needle valve and metering needle slightly on the rich side of the best rpm setting, as a safety measure. Finally, beyond the normal break-in period, a slight readjustment toward a leaner needle setting may be required to maintain maximum performance.

Note: Please regard the standard positions in the instruction manual as just a guide. Positions will vary due to the fuel and silencer used. In general, if a fuel containing less nitromethane is used, the needle valve will need to be closed further. Remember, closing the needle valve too far can cause rusting and damage to the engine.

Attention: It is vitally important to set the throttle at the correct position before starting the engine. If the engine is allowed to run with the throttle too far open under ”no-load” conditions (i.e. with the driving wheels not in contact with the ground) it will rapidly overheat and may be seriously damaged.

CARE AND MAINTENANCE

1. The minute particles of foreign matter, that are present in any fuel may, by accumulating and partially obstructing fuel flow, cause engine performance to become erratic and unreliable. O.S. ‘Super-Filters’ (large and small) are available, as optional extras, to deal with this problem. One of these filters installed to the pickup tube inside your refueling container will prevent the entry of foreign material into the fuel tank. It is also recommended that a good in-line filter be installed between the tank and carburetor.

2. Do not forget to clean the filters regularly to remove dirt and lint that accumulate on the filter screens. Also, clean the carburetor itself occasionally.

3. At the end of each operating session, drain out any fuel that may remain in the fuel tank. Afterward, energize the glow plug and try to restart the engine, to burn off any fuel that may remain inside the engine. Repeat this procedure until the engine fails to fire. Do this while the engine is still warm.

4. Then, inject some after-run oil into the engine, and rotate the engine with an electric starter for 4 to 5 seconds to distribute the oil to all the working parts.
   Note: Do not inject after-run oil into the carburetor as this may cause the O-rings inside the carburetor to deteriorate. These procedures will reduce the risks of starting difficulties or corrosion after a period of storage.

5. Finally, when cleaning the exterior of the engine, use methanol or a household cleaning agent. Do not use gasoline, kerosene, or any petroleum-based chemical which can damage silicone fuel tubing.

REMOVING DIRT/STAIN
Dirt and stain stuck on the engine and silencer/manifold cause a lowering heat dissipation effect. When dirt and stain are detected, remove the engine from the chassis and clean it with alcohol.

INSTALLING DUST CAPS
When storing the engine, install the cap on the exhaust port, carburetor, etc. to prevent dust from entering the engine.

CHECKING THE ENGINE
If the engine will not develop normal performance after a long time running due to the wearing of parts. It is suggested to replace necessary parts when the following symptoms are detected.

• Engine sound changes and easily overheats.
• Power has dropped extremely.
• Idle is unstable and/or the engine tends to stop at idle.

In most cases, ball bearings, cylinder & piston assembly, connecting rods, and/or crankcases have become worn. Check the parts carefully and replace them if necessary.

O.S. GENUINE PARTS & ACCESSORIES

• T SERIES PLUG

  • RP6 (71642060)
  • RP7 (71642070)
  • P3 (71641300)
  • P4 (71641400)
  • P5 (71641500)

• O.S. SPEED T SERIES PLUG

  • RP6 (71642740)
  • RP7 (71642750)

• CARBURETOR REDUCER (W/ “O” Ring, Aluminum)

  • 6 (71533260)
  • 6II (71533261)
  • 6.5 (71533265)
  • 6.5II(71533865)
  • 7 (71533270)
  • 8 (71533280)
  • 8.5 (71533085)
  • 9 (71533290)

• MB01-75(M2000SC) EXHAUST HEADER PIPE ASSEMBLY (72106440)
  MB01-80(M2002SC) EXHAUST HEADER PIPE ASSEMBLY (72106480)

• MB01-85(M2004SC) EXHAUST HEADER PIPE ASSEMBLY (72106910)

• INDUCTION SILENCER (72414000)

  • Induction Silencer Filter (3pcs.) (72414100)

• O.S. SPEED FILTER OIL (ON-ROAD) (20ml) (72414210)

• SUPER AIR CLEANER 204 (72415000)

  • 204 Filter Element (4pcs.) (72415200)

• PRESSURE CHAMBER SET (71550000)

• O.S. SPEED CLUTCH BEARING (1050ZZ 4pcs.)(71550001)

• O.S. SPEED CLUTCH BEARING (1050ZZ 10pcs.)(71550002)

• O.S. SPEED CILICONE TUBE (72506100) 2.5mm x 1000mm

• O.S. SPEED EXHAUST SEAL RING (2pcs.) (22826140)

• O.S. SPEED EXHAUST SEAL RING (10pcs.) (22826145)

• O.S. SPEED DUST CAP SET FOR 12-30 CLASS 3mm(2pcs.) / 16mm(2pcs.) / 18mm(1pc.) (22884254)

• DUST CAP SET 3mm (5pcs.) (73300305)

• DUST CAP SET 16mm (3pcs.) (73301612)

• DUST CAP SET 18mm (3pcs.) (73301812)

• O.S. SPEED MAINTENANCE OIL (71430010)

• O.S. SPEED TOOLS

ENGINE EXPLODED VIEW

CAP SCREW SETS (10pcs./set)

COMBO SET

THREE VIEW DRAWING
Dimensions (mm)

SPECIFICATIONS

• Displacement: 3.49 cc / 0.213 cu.in.
• Bore: 16.08 mm / 0.633 in.
• Stroke: 17.20 mm / 0.677 in.
• Output: 2.65 ps / 2.61 hp / 34,000 r.p.m.
• Practical R.P.M.: 4,000-42,000 r.p.m.
• Weight: 362 g / 12.77 oz. (Engine)

ENGINE PARTS LIST

Marked parts are available only for limited period (one year after finishing the production).

CARBURETOR EXPLODED VIEW

CARBURETOR PARTS LIST

Marked parts are available only for limited period (one year after finishing the production).

6-15 3-Chome Imagawa Higashisumiyoshi-ku
Osaka 546-0003, Japan
TEL. (06)6702-0225
FAX. (06)6704-2722
http://www.os-engines.co.jp
Copyright 2022 by O.S. Engines Mfg. Co., Ltd. All rights reserved. Printed in JAPAN.

References

• O.S.ENGINES MFG.CO.,LTD.

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