O.S. Speed 21XZ-B Spec II User Manual

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)

O.S. Speed 21XZ-B Spec II Specifications

General

Fuel Type	Glow Fuel
Displacement	3.49 cc
Stroke	16.80 mm
Glow Plug	Turbo
Carburetor	Rotary
Fuel	Nitromethane-based

Summary

Safety Instructions and Warnings

General Warnings and Precautions

Covers serious injury risks from engine misuse, poisonous and flammable fuel.

Operational Cautions

Warns against enclosed spaces and specifies intended use for model cars.

Engine Construction and Initial Notes

Engine Construction Details

Explains normal piston tightness when cold and the importance of operating temperature.

Electric Starter Usage Precautions

Advises against over-priming to prevent hydraulic lock and engine damage.

Operation Notes and Warranty

Warranty Information

States warranty is limited and void if damage occurs during running.

Safe Operating Practices

Prohibits public street use, running near pedestrians, and in confined areas.

Engine Overview and Accessories

Notes carburetor fitment and provides an overview of the O.S. SPEED 21XZ-B engine.

Instruction Manual - General Guidelines

Silencer and Hearing Protection

Recommends effective silencers to prevent hearing damage from noisy exhausts.

Safety Gear and Lead Checks

Advises wearing safety glasses and securing glowplug clips/battery leads.

Onlooker Safety and Screw Tightness

Emphasizes keeping onlookers back and checking screw tightness for safety.

Engine Stopping Procedures

Details how to stop the engine using the transmitter or fuel line pinch.

Restart Prevention Warning

Warns of potential abrupt restart if engine is rotated while warm without glowplug.

Carburetor Controls and Adjustment

Carburetor Parts and Standard Positions

Details carburetor controls: Needle Valve, Mixture Control Valve, Metering Needle, Throttle Stop Screw.

Carburetor Installation

Provides instructions on securing the carburetor to the engine's intake boss.

Engine Installation Guidelines

Ensures proper mounting to prevent crankcase distortion and erratic running.

Starting the Engine and Running-In

Running-In Procedure Overview

Explains running-in is for achieving near-actual conditions and avoiding prolonged low speed.

Pressurized Fuel System

Recommends pressurized fuel feed systems for stable fuel supply to the carburetor.

Starting Steps

Details steps for connecting battery, starting engine, and adjusting for non-start.

Warm-up and Initial Running

Describes warming up with rich mixture and advises on throttle position to prevent overheating.

Break-in Fuel Consumption

Guides gradual full throttle running over approximately 2 liters of fuel consumption.

Carburetor Adjustment

Needle Valve Adjustment

Adjusts air/fuel ratio at maximum RPM for optimal straight-line speed.

Metering Needle Adjustment

Adjusts idle and acceleration feeling for smooth throttle response.

Throttle Stop Screw Adjustment

Sets the minimum idle speed by adjusting the throttle opening when closed.

Optimum Mixture Control Position

Achieves light smoke during high speed and smooth RPM increase during acceleration.

Care and Maintenance

Fuel Filter Maintenance

Recommends cleaning filters regularly to prevent dirt accumulation and ensure fuel flow.

Post-Operation Fuel Drainage

Details draining fuel and running engine to burn off residual fuel for storage.

After-Run Oil Injection

Injects after-run oil into engine (not carburetor) to protect parts during storage.

Exterior Cleaning

Use methanol or household cleaner for exterior, avoid petroleum-based chemicals.

Dirt/Stain Removal

Removes dirt and stains from engine and silencer for better heat dissipation.

Dust Cap Installation

Installs caps on exhaust and carburetor ports to prevent dust entry during storage.

Engine Wear and Part Replacement

Identifies symptoms of wear and suggests replacing parts like bearings or piston/cylinder.

Parts and Accessories

O.S. Glow Plugs and Carburetor Reducers

Lists specific O.S. glow plug types and carburetor reducer sizes.

Tuned Silencer Sets

Details available tuned silencer sets and associated parts like seal rings and springs.

Flywheel Sets and Air Cleaners

Lists flywheel sets for different models and super air cleaner components.

Carburetor Repair Kits

Provides part numbers for O.S. SPEED carburetor repair kits.

Clutch Bearings and Silicone Tubes

Lists clutch bearings in different quantities and silicone fuel tubing.

Specialized Parts and Caps

Details exhaust seal rings, piston pin retainers, and various dust cap sets.

Tools and Drivers

Lists essential tools like clutch wrench, flywheel puller, plug wrench, and driver sets.

Engine Exploded Views and Specifications

Engine Exploded View

Diagram showing all engine parts with numerical and code references.

Carburetor Exploded View

Diagram illustrating all carburetor components with references.

Three View Drawing

Provides dimensional drawings of the engine from different perspectives.

Engine Specifications

Lists key engine specifications like displacement, bore, stroke, and output.

Engine Parts List

Comprehensive list of engine parts with part numbers and descriptions.

Carburetor Parts List

Detailed list of carburetor components with part numbers.