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It is of vital importance, before attempting to operate your 

engine, 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 with 

the controls and other features of the engine.

SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE

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

NOTES

These cover events which might involve serious 

(in extreme circumstances, even fatal) injury.

These cover the many other possibilities, generally less 

obvious sources of danger, but which, under certain 

circumstances, may also cause damage or injury.

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. 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.

WARNINGS

NOTES

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.

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.
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.

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 cause annoyance to 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.

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.

To stop the engine, fully retard the throttle stick and 

trim 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.

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 the loose screws and nuts 

often causes the parts breakage that is capable of 

harming you. 

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.

Piston

Cylinder

Liner

Crankshaft

Near TDC

Slight taper

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

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 any pumped out fuel from getting into 

your eyes.

As delivered, the engine has the carburetor 

lightly fit into its intake. Secure it changing its 

angle according to the car chassis.

NOTE

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.
Please do not run where loud noises can disturb 

others, such as hospitals and residential areas.

While Operating

ABOUT THE ENGINE

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 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.  

Items necessary for starting

TOOLS, ACCESSORIES, etc.

The following items are necessary for operating the engine.

FUEL FILTER

To installed in the fuel line between fuel 

tank and carburetor to prevent foreign 

matter from entering the carburetor.

GLOWPLUG IGNITER

Commercialy 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. 

TOOLS

O.S. SPEED DRIVER TOOLS

O.S. SPEED PLUG WRENCH

O.S. SPEED

CLUTCH WRENCH & ADJUSTER

O.S. SPEED FLYWHEEL KEY

O.S. SPEED FLYWHEEL PULLER

ABOUT THE WARRANTY

NOTES ON OPERATION

Since this is a special SPEED version, individual 

special parts are available only for limited period 

(one year after finishing the production).

Also, the engine is free of warranty due to damage 

and/or wear occurred during running.

The O.S. SPEED 21XZ-B is a high performance 

engine produced by O.S.’s SPEED TEAM technicians.

Based on the MAX-21XZ-B, major parts have been 

refined to have a powerful potential equal to more 

expensive specially tuned or modified engines.

Glow Plug P3  T-type head (Turbo head)  

1piece

Exhaust Seal Ring  1piece

Dust Cap   3,  16,  18  1piece each 

Carburetor Reducer (RED)

6mm & 7mm 1piece each  (w/ "O" Ring)

(Hot Type)

Standard accessories

The connection between the fuel tank and the engine. 

2.5mm ID

O.S. SPEED SILICONE FUEL LINE (optional extra)

Summary of Contents for 21XZ-B Spec II

Page 1: ... compression WITHOUT the glowplug battery being reconnected 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 the loose screws and nuts often causes the parts breakage that is capable of harming you ENGINE CONSTRUCTION With this engine the piston will feel tight at the top of its st...

Page 2: ...o Insulator The Mixture Control Valve For adjusting acceleration feeling Adjusting range should be within 1 turn 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 1 2 Rotate the retainer nut gently until it stops Tighten a further 120 180 Rotate the retainer...

Page 3: ...O S SPEED HEX WRENCH DRIVER 3 0 O S SPEED HEX BALL WRENCH DRIVER 2 0 O S SPEED HEX BALL WRENCH DRIVER 2 5 O S SPEED FLAT HEAD SCREWDRIVER 3 0 O S SPEED NUT DRIVER 5 5 O S SPEED NUT DRIVER 6 0 O S SPEED NUT DRIVER 7 0 O S SPEED DRIVER TOOLS Code No Description 71414015 71414020 71414025 71414030 71414120 71414125 71414230 71414355 71414360 71414370 O S SPEED HEX WRENCH TIP ONLY 1 5 O S SPEED HEX WR...

Page 4: ... O Ring Needle Assembly O Ring 2pcs Needle Holder Assembly Fuel Inlet No 15 Throttle Stop Screw O Ring 2pcs Mixture Control Valve Assembly O Ring L 2pcs O Ring S 2pcs Carburetor Body w Thermo Insulator Thermo Insulator Carburetor Rubber Gasket Carburetor Sealing Washer marked parts are available only for limited period one year after finishing the production Outer Head Inner Head Head Gasket 0 2mm...

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