O.S. Engines 21XZ-M User Manual
It is of vital importance, before attempting to operate
your eng ine, to read the gene ral 'SAFETY
INSTRUCTIONS AND WARNINGS' section on
pages 2-5 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.
It is suggested that any instructions supplied with
the vehicle, radio control equipment, etc., are
accessible for checking at the same time.
1
CONTENTS
SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE
ENGINE CONSTRUCTION, NOTES WHEN
APPLYING AN ELECTRIC STARTER,
NOTES ON OPERATION
ABOUT THE ENGINE,
TOOLS, ACCESSORIES, etc.
BASIC ENGINE PARTS,
CARBURETOR CONTROLS
GLOWPLUG
INSTALLATION
STARTING THE ENGINE &
RUNNING-IN ('Breaking-in)
2-5
6-8
9-11
15
36-37
FINAL ADJUSTMENT
CARE AND MAINTENANCE
TROUBLE SHOOTING
ENGINE EXPLODED VIEWS &
PARTS LIST
CARBURETOR EXPLODED VIEW &
PARTS LIST
O.S. GENUINE PARTS & ACCESSORIES
THREE VIEW DRAWING
28-31
12-14
19-23
34-35
24-25
26-27
38
16-18
32-33
2
!
!
Remember that your engine is not a "toy", but a highly efficient internalcombustion machine whose power is capable of harming you, or others, if it is
misused.
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.
SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE
The advice which follows applies basically to ALL MODEL ENGINES and is
grouped under two headings according to the degree of damage or danger
which might arise through misuse or neglect.
WARNINGS
NOTES
Th e se co v er ev e nts wh ich
mig h t inv o lve se rious (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.
3
!
WARNINGS
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.
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.
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 touch, or allow any
object to come into contact
with, the rotating propeller and
do not crouch over the engine
when it is running.
4
!
This engine was designed for model boats.
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 most powerful
high-speed engines) may eventually impair
your hearing and such noise is also likely to
cause annoyance to others over a wide area.
Take care that the glowplug clip or battery
leads do not come into contact with the propeller or any other rotating parts. Also check
that the linkage to the throttle arm is secure.
If your engine does not have a built-in recoil
starter, use an electric starter. The wearing of
safety glasses is also strongly recommended.
When handling the boat immediately prior to
launching, be especially cautious.
Keep the propeller and other rotating parts
away from you.
NOTES
For their safety, ke ep al l onlooke rs
(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 the loose
screws and nuts often causes the parts
breakage that is capable of harming you.
5
!
Adjust the throttle linkage so that the
engine stops when the throttle stick and
trim lever on the transmitter are fully
retarded. Alternatively, the engine may be
stopped by cutting off the fuel supply.
Never try to stop the engine physically.
Warning! Immediately after a glowplugignition 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.
NOTES
6
Piston
Cylinder Liner
Crankshaft
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.
Near TDC
Slight taper
When the engine is cold.
When the engine is hot.
7
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.
8
GUARANTEE
This engine is constructed from the very
best materials 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 are beyond a
manufacturer's control. Accordingly, we
regret that it is not possible to extend
our usual warranty terms to this
particular engine -i.e. no guarantee is
offered against material wear, or damage
resulting from, actual use.
As delivered, the engine has the
carburetor lightly fit into its intake.
Secure it changing its angle according
to the hull.
NOTE
NOTES ON OPERATION
We do not recommend running your boat
on the sea, or in any other saltwater
environment. Under such conditions, it is
difficult to prevent the engine from
becoming corroded and, eventu ally,
inoperative.
NOTE
9
ABOUT THE ENGINE
Standard accessories
Glow Plug RP7 For T-type head
(Turbo head) 1piece
Cylinder-head gasket
(0.2mm) 1 sheet
Exhaust Seal Ring 1piece
Dust Cap 3, 16, 18
1piece each
The MAX-21XZ-M is designed expressly for
21 class boat racing, basing on the race
proven MAX-21XZ-R on road car racing
engine.
The big bore of 10mm 21D carburetor
copes with high nitro fuel.
This engine offers high racing potential
maintaining O.S. traditional easy-to-handle
characteristics.
Head Gaskets
The engine comes with a o.2mm and 0.1mm
thick head gasket installed. If you find the
following symptoms after running the engine,
add a 0.2mm thick gasket supplied.
With the appropriate needle setting, engine
r.p.m. drop and power loss during running.
Composition and proportion of lubricant in the
fuel may affect the symptoms.
Glow plug burns out frequently.
10
FUEL
Generally, it is suggested that the user selects a fuel
that is commercially available for model two-stroke
engines and contains 10-30% nitromethane. As a
starting point, we recommend a fuel containing 20%
nitromethane, changing to a fuel containing more
nitro if necessary. 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
!
REMINDER!
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.
TOOLS, ACCESSORIES, etc.
The following items are necessary for operating the engine.
!
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.
PROPELLER
Use well balanced propellers only. As the ideal
diameter, pitch and shape vary according to the
size, weight and type of model, final selection
can be made after practical experiment. As a
starting point, suggested propeller diameter is
41-43mm with a pitch/dia ratio of 1.0-1.1 for indrive Vee type hulls, 40-45mm with a pitch/dia.
ratio of 1.2-1.6 for out-drive Vee type
hulls and 44-46mm with a pitch/dia.
ratio of 1.4-1.6 for hydroplanes.
NOTE
Never use a propeller that has even
slight damage.
11
TOOLS
GLOWPLUG IGNITER
Commercialy available handy glowplug
heater in which the glowplug battery
and battery leads are integrated.
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.
REMINDER!
!
SILICONE TUBING
This is required for the connection between the
fuel tank and engine, also for the water cooling
system. Inner dia. of 2.3-2.5mm
and outer dia. of 5-5.5mm would be
suitable.
ELECTRIC STARTER AND STARTER BATTERY
Use a 12-volt electric starter
with suitable battery for starting the engine.
Necessary for starting the engine.
It is suggested to keep a starter rope as a reserve.
STARTER BELT
Install a filter to the outlet tube of your
refuelling container to prevent entry of
foreign matter into the fuel tank.
SUPER FILTER (L)
(Option)
O.S. SPEED DRIVER TOOLS
O.S. SPEED PLUG WRENCH
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