BASIC ENGINE PARTS

O.S. SPEED R21 SHIMO EDITION 2 Combo Set
It is of vital importance, before attempting to operate yourengine, to read the general 'SAFETY INSTRUCTIONS
AND WARNINGS' in the following section and to strictly
adhere to the advice contained therein.
Also, please study the entire contents of this
instruction manual, so as to familiarize yourself withthe controls and other features of the engine.

SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE

Remember that your engine is not a " toy ", but ahighly efficient internal-combustion machine whose
power is capable of harming you, or others, if it ismisused or abused. As owner, you, alone, areresponsible for the safe operation of your engine, so
act with discretion and care at all times. If at somefuture date, your O.S. engine is acquired by anotherperson, we would respectfully request that these
instructions are also passed on to its new owner.
The advice which follows is grouped under twoheadings 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 lessobvious sources of danger, but which, under certain
circumstances, may also cause damage or injury.
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 slighttaper. The piston and cylinder are designed toachieve a perfect running clearance when theyreach operating temperature.
Near TDC

CylinderLiner

PistonCrankshaft
Slight taper

Model engine fuel is poisonous. Do notallow 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.

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.

Take care that the glowplug clip or battery leads do
not come into contact with rotating parts. Also checkthat the linkage to the throttle arm is secure.

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 inan 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.
NOTES ON OPERATIONGUARANTEEThis engine is constructed from the very bestmaterials available and to the very highest
engineering standards, using the most advanced
precision machinery. However, the extremely
high stresses imposed by car racing operation
under very severe conditions, as well as stresses
which are exacerbated by the use of powerful
fuels containing very high concentrations of
nitromethane, constitute hazards which arebeyond a manufacturer's control. Accordingly,
we regret that it is not possible to extend ourusual warranty terms to this particular engine -i.e.
no guarantee is offered against material wear, or
damage resulting therefrom, in actual use.
While Operating
Please do not run on a public street, this could
cause serious accidents, personal injuries
and/or propetry damage.
Please do not run near pedestrians or small children.
Please do not run in small or confined areas.

NOTES WHEN APPLYING AN ELECTRIC STARTER
Do not over-prime. This could cause ahydraulic 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 toprevent any pumped out fuel from getting into
your eyes.

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

We have developed O.S.SPEED R21 Shimo edition
collaborated with Takaaki Shimo, a multiple podium
winner of the IFMAR 1/8 Racing World Championship.
The cooling head and 8.5mm carburetor restrictor isanodized in the special color ; champagne gold.
The inner head is o-ring-sealed to prevent dust fromcoming in.
The crankshaft is modified to meet his preference,smooth power transition from bottom to the top speed.
For the first time we make the combination of TR02
silencer with MR03-WC manifold to dedicate to thisspecial edition.

Carburetor Type
21M2(B) SHIMO2

ExhaustThe wearing of safety glasses is also strongly
recommended.

Cover Plate

Before starting the engine, always check thetightness of all the screws and nuts especially thoseof joint and movable parts such as throttle arm.
Missing retightening the loose screws and nuts
often causes the parts breakage that is capable ofharming you.
To stop the engine, fully retard the throttle stick andtrim lever on the trans-mitter, 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.
Standard accessories
T Series Plug RP7 (Turbo head) 1pc.
TR02 EFRA2165 Tuned Silencer
Joint Spring (3pcs.)
Exhaust Seal Ring (1pc.)
MR03-WC Exhaust Header Pipe
Exhaust Header Pipe Spring (102mm 2pcs.)
Exhaust Seal Ring (1pc.)
Flywheel Collet 1pc.

Exhaust Seal Ring 1pc.
3, 16, 18 1pc. each

Instruction Manual

Crankshaft
Mounting Lugs

INSTALLATION OF THE STANDARD ACCESSORIESINSTALLATION OF THE TAPER COLLET
Insert the taper collet on the crankshaft, taking care
not to push the crankshaft back so that it contacts thecoverplate face.
Cover Plate

Taper Collet
ABOUT THE HEAD GASKETThe engine is installed with a 0.1mm thick and a
0.15mm thick gasket for 25% nitro fuel when it leaves
the factory. Adjust the total thickness according toatmospheric temperature, humidity and glowplug
used.

Four adjustable controls are provided on thiscarburetor.
Ball Link
Carburetor Reducer

Mixture Control Valve

Throttle Stop Needle Valve
Dust Cover
Metering Needle Screw
The Needle-Valve:
For adjusting air/fuel ratio (air-fuel mixture) at maximum
rpm (fully opened throttle).
Close(Clockwise)

Needle Valve

Open(Counter-clockwise)

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

3 turns opened from the fully closed position.

FUEL PUMP
For filling the fuel tank, a simple, polyethylene"squeeze" bottle, with a suitable spout, is required.
O.S. SPEED SILICONE FUEL LINE (optional extra)
The connection between the fuel tank and the engine.
2.5mm ID
O.S. SPEED TOOLS (optional extra)[Standard Position][Fully closed position]

Turn the needle-valve clockwise until it stops.
This is the fully closed position.
Do not force it to turn further.

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

Flush with the carburetor body.

Carburetor Body
Slide Valve
Note:
Sketch shows the carburetor reducer removed.
NOTE: While the Mixture Control Valve and theMetering Valve are set at the standard position
when the engine leaves the factory, readjustment
may be necessary, occasionally to allow forchanges 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 installedin the intake boss. Secure it as follows.
Rotate the retainer screw
gently until it stops.
Tighten a further
120-180

Retaining
Screw"O" Ring

Pull out"O" Ring

1. Loosen the retainer screw, rotate the carburetor to its
correct position and make sure that it is pressed welldown into the intake boss, compressing the rubber
gasket, before retightening screw.
2. Rotate the retaining screw gently until it stops, thentighten a further 120-180 , and no more.
Do not overtighten the screw as this will damage the
carburetor body.
Note
Be careful not to damage the O rings whenremoving the carburetor retainer from the engine.
First, remove the Retaining screw, then pull out
each retainer. Do not push the retainers in or the O
rings will get damage.
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 existingholes in the engine mount do not align perfectly withengine mounting lugs, enlarge them slightly with aneedle-file so that screws are in alignment with themounting holes.

Do not allow bottomof crankcase totouch chassis.

Mixture Control Valve

Carburetor Body

STARTING THE ENGINE & RUNNING-IN ('Breaking-in)

Running- in is a procedure for an engine to comeclose 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 resultin the oil in the fuel becoming gelled and thepiston/liner becoming stuck together.
PRESSURIZED FUEL SYSTEM
It is recommended that a muffler pressurized fuelfeed system be used so that the fuel may be stably
fed to the carburetor.
The following procedure is suitable when a fuelcontaining 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 eachlinkage moves correctly.

CARBURETOR CONTROLS STANDARD POSITIONS(POSITIONS WHEN THE ENGINE LEAVES THE FACTORY)FUEL FILTER
To installed in the fuel line between fuel tank andcarburetor to prevent foreign matter from entering the
carburetor.

STARTER BOX
For starting the engine.

[Standard Position]
Approx 0.5mm

Crankcase
Crankshaft Bearing (Front)

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 fuelthat is commercially available for model two-stroke
engines. When the brand of fuel is changed, or the nitro
content increased, 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.

[Standard Position]
open one rotation (0.5mm out)
from the flush position with theball link body
Metering Needle
Slide Valve
Carburetor Body
The Throttle Stop Screw:
For setting the minimum idle speed:

For their safety, keep all onlookers (especially smallchildren) well back (at least 20 feet or 6 meters)
when preparing your model for running.

Dust Cap Set

The Metering Needle:
For adjusting idle and acceleration feeling.
Ball Link

Install an effective silencer (muffler). Frequent close
exposure to a noisy exhaust (especially in the caseof the more powerful highspeed engines) may
eventually impair your hearing and such noise isalso likely to cause annoyance to others over a widearea.

WARNINGS

Please do not run where loud noises can disturb
others, such as hospitals and residential areas.

When the engine is cold. When the engine is hot.

Outer Head

Chamfer inside edges of bearers.

3. Make sure rotating direction of the starter box iscorrect (counter-clockwise seen from the front edgeof the crankshaft), and turn the engine with thestarter box to draw fuel into the engine.
4. Connect glowplug battery lead to heat the plug andstart 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 thestandard position.
Set the throttle opening alittle wider (approx. 1mm)
than the standard setting
by adjusting the Throttle
Stop Screw.

approx 1mm

5. When the engine starts, warm it up by repeatedly
increasing the rpm to medium speed and backagain 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.
Attention:
It is vitally important to set thethrottle 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 theground) it will rapidly over-heat and may beseriously damaged.
6. 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 ataround mid speed, the mixture is too rich. Close theneedle-valve 30°.
If the engine still stalls, close the metering needle
30°. Run the car on the track until one tank of fuelhas been consumed, then close the needle-valve
very little (within 10°).
7. 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.
Now the RUNNING-IN (Breaking-in) is completed.

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 thethrottle to idle speed and shut it offcompletely with the trim lever on thetransmitter then cut off the fuelsupply by pinching the fuel delivery
tube to the carburetor.

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

FuelLess fuelOpen

More fuel

Close

Less fuel1. NEEDLE VALVE ADJUSTMENT
Run the vehicle (with throttle fully open) over the
longest available straight course a few times toobserve the model’s speed. Return the vehicle to thestarting point and close the Needle-valve 10~15°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, stopthe vehicle and reopen the Needle-valve 30°.
2. METERING NEEDLE ADJUSTMENT
After setting the Needle-valve at optimum position,
run the vehicle a few times at the straightway, andstop the vehicle. With the engine still 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 isprobable that the idle mixture is too rich. In thiscase, turn the Metering needle clockwise 30~45°.
If, on the other hand, the engine tends to speed up
momentarily with little smoke 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 30~45°.

3. THROTTLE STOP SCREW ADJUSTMENT
If the engine runs too fast with the throttle closed, thethrottle 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
increase 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 boththe needle-valve and metering needle slightly on the richside 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 berequired to maintain maximum performance.
Note:
Please regard the standard positions in the
instruction manual as just a guide. Positions willvary due to the fuel and silencer used. In general,
if a fuel containing less nitromenthane is used, theneedlevalve will need to be closed further.
Remember, closing the needlevalve too far cancause rusting and damage to the engine.
CARE AND MAINTENANCE
1. The minute particles of foreign matter, that are present inany 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 foreignmaterial into the fuel tank. It is also recommended that agood in-line filter be installed between the tank andcarburetor.

Note:
Do not inject after-run oil into the carburetor as
this may cause the O-rings inside the carburetor todeteriorate. These procedures will reduce the risksof starting difficulties or corrosion after a period ofstorage.
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.
Note:
Crankshaft of this engine is filled with silicone.
Do not use light oil nor kerosene, etc. forwashing, or the silicone will swell. Use alcoholor fuel for washing and dry it completely.

Dirt and dust may lodge inmarked places.

Type of screw
C...Cap Screw

O.S. SPEED T SERIES PLUG
RP6 (71642740) RP7 (71642750)

C.M3x18

TR01 EFRA2098 (T-2080SCII) COMPLETE SET(72106852)
TR01 EFRA2098 (T-2080SC) Tuned Silencer
Assembly (72106851)

1

MR02 Exhaust Header Pipe Assembly(72106490)
TR02 EFRA2165 COMPLETE SET (72106970)
TR02 EFRA2165 Tuned Silencer Assembly

2-1

MR02 Exhaust Header Pipe Assembly(72106490)

3(72106971)

INDUCTION SILENCER (72414000)
Induction Silencer Filter (3pcs.) (72414100)

4-3

5

O.S. SPEED FLYWHEEL COLLET (2pcs.)(71801110)

INATALLING DUST CAPS
When storing the engine, install the cap on the exhaust
port, carburetor, etc. to prevent dust from entering theengine.
CHECKING THE ENGINE

If the engine will not develop normal performance after
long time running due to wearing of parts. It is suggested
to replace necessary parts when the following symptoms
are detected.
Engine sound changes and easily overheats.

4-4

10

11

72106990
72101272

1222884250

Description
Outer HeadInner HeadInner Head "O" Ring (RED)
Head Gasket Set (0.1mm / 0.15mm)
Built-Up Parts Set
Cylinder & Piston Assembly
Piston Pin
O.S. SPEED Piston Pin Retainer 2 (6pcs.)
Connecting Rod w/piston pin retainers (3pcs.)
Carburetor Complete (Type 21M2(B) SHIMO2)
Carburetor Retainer Assembly"O" Ring (2pcs.)
Crankshaft Ball Bearing (Front)
Crankcase
Crankshaft Ball Bearing (Rear)
Crankshaft
Cover Gasket
Cover Plate
T Series Plug RP7
Flywheel Collet
Exhaust Seal Ring
TR02 EFRA2165 Tuned Silencer Assembly
Joint Spring (3pcs.)
Exhaust Seal Ring
MR03-WC Exhaust Header Pipe Assembly
Header Pipe Spring (2pcs.)
Exhaust Seal Ring
Dust Cap Set ( 3, 16, 18 1pc. each)

9

6

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

Code No.
2DJ04000
2C604100
2BN04180
2A004160
2DJ03010
2DJ03000
22016000
2AP17000
23755024
2DJ81000
23981740
24881824
23731000
2DJ01000
23730020
2DJ02000
23107100
2A007000
71642070

72106971
72106042

4-2

C.M2.6x18

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

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

C.M2.6x7

4-1

SUPER AIR CLEANER 202 ASSEMBLY
On-road Type (72412000)
202 Cleaner Body (72412100)
202 Filter Element (4pcs.) (72412200)

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

2

4ON-ROAD FILTER OIL (20ml) (72414200)

PRESSURE CHAMBER SET (71550000)

REMOVING DIRT/STAIN

No.
1
2
2-1
3
4
4-1
4-2
4-3
4-4
5
6
6-1
7
8
9
10
11
12

8

7

6-1
CARBURETOR EXPLODED VIEW & PARTS LIST

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

CAP SCREW SETS (10pcs./set)
Code No.

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

Size

Type of screw

Pcs. used in an engine

79871020 M2.6x7 Cover Plate Retaining Screw (4pcs.)
79871055 M2.6x18 Carburetor Retainer Retaining Screw (1pc.)
79871180 M3x18 Cylinder Head Retaining Screw (4pcs.)

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

5

2-1

5-1

8
8-1

3

DUST CAP SET 3mm (5pcs.) (73300305)

O.S. SPEED MAINTENANCE OIL (71430010)

S.M3x3

1-1
1-2

THREE VIEW DRAWING
Dimensions (mm)

1

10
10-1

4-1

DUST CAP SET 18mm (3pcs.) (73301812)
O.S. SPEED TOOLS

9

4

3-1

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

C...Cap Screw S...Set Screw

2

5-1

7
6

11

Power has dropped extremely.
Idle is unstable and/or engine tends to stop at idle.
In most cases, ball bearings, cylinder & piston assembly,
connecting rod and/or crankcase have become worn.
Check the parts carefully and replace them if necessary.

75.6

More fuelClose

4. Then, inject some after-run oil into the engine, androtate the engine with an electric starter for 4 to 5
seconds to distribute the oil to all the working parts.

RP7 (71642070)

ENGINE EXPLODED VIEW
& PARTS LIST

UNF1/4-28

28

Open

Metering Needle

O.S. GENUINE PARTS & ACCESSORIEST SERIES PLUG
RP6 (71642060)
RP8 (71642080)

15.6

Needle Valve

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

31.6
45

29.5

64.5

4- 3.3SPECIFICATIONS
Displacement
Bore
StrokeOutputPractical R.P.M.
Weight3.49 cc / 0.213 cu.in.
16.08mm / 0.633 in.
17.20mm / 0.677 in.
2.8 ps / 2.76 hp / 35,000 r.p.m.
4,000-45,000 r.p.m.
340g / 11.99 oz. (Engine)

37

FINAL ADJUSTMENT

Final adjustment should be carried out only after therunning-in has been completed.

21

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.
The specifications are subject to alteration for improvement without notice.

No. Code No.
1 22082600
1-1 46066319
1-2 22781800
2 22082970
2-1 46066319
3 22082940
3-1 22082950
4 22848160
4-1 27881820
5 71533885
5-1 22615000
6 22082110
7 22082200
8 2A081610
8-1 27881820
9 23981520
10 23781400
10-1 26381501
11 29015019

http://www.os-engines.co.jp

Description
Mixture Control Valve Assembly"O" Ring (L) (2pcs.)"O" Ring (S) (2pcs.)
Needle Assembly"O" Ring (2pcs.)
Needle Holder Assembly
No.15 Universal Nipple Assembly
Throttle Stop Screw"O" Ring (S) (2pcs.)
Carburetor Reducer (8.5mm Champagne Gold)"O" Ring (1pc.)
Carburetor Body
Slide Valve
Metering Needle Assembly"O" Ring (S) (2pcs.)
Dust CoverBall Link No.3
Set Screw (1pc.)
Carburetor Rubber Gasket

6-15 3-Chome Imagawa Higashisumiyoshi-ku
Osaka 546-0003, Japan TEL. (06)6702-0225
FAX. (06)6704-2722

Copyright 2021 by O.S. Engines Mfg. Co., Ltd. All rights reserved. Printed in JAPAN.

60093800

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