O.S. Engines 21VZ-M User Manual
It is of vital importance, before attempting to
operate your engine, to read the general
'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.
SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE
ENGINE CONSTRUCTION, NOTES ON
INSTALLING FLYWHEEL, NOTES WHEN
APPLYING AN ELECTRIC STARTER
INSTRUCTIONS,
TOOLS, ACCESSORIES, etc.
BASIC ENGINE PARTS, INSTALLATION OF
THE ACCESSORIES SUPPLIED,
INSTALLATION OF REPLACEMENT PARTS
INSTALLATION
GLOWPLUG, CARBURETOR CONTROLS
STARTING THE ENGINE &
RUNNING-IN ('Breaking-in)
CONTENTS
2-5
6-8
9-11
12-14
15
16-18
19-22
FINAL ADJUSTMENT
CARBURETOR CLEANLINESS,
CARE AND MAINTENANCE
CHECKING THE ENGINE, GUARANTEE
TROUBLE SHOOTING
ENGINE EXPLODED VIEWS &
PARTS LIST
CARBURETOR EXPLODED VIEW &
PARTS LIST
O.S. GENUINE PARTS & ACCESSORIES
THREE VIEW DRAWING
1
23-24
25-26
27
28-31
32-33
34-35
36-37
38
SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE
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.
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
!
These cover events which
might involve serious (in
extreme circumstances, even
fatal) injury.
WARNINGS
!
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.
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.
NOTES
!
These cover the many other
possibilities, generally less obvious
sources of danger, but which, under
certain circumstances, may also
cause damage or injury.
2
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.
3
NOTES
!
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 ov er a wide area.
For their safety, keep all onlookers
(especially small children) well back (at
least 20 feet or 6 meters) when preparing
your model for running.
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.
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.
4
NOTES
!
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.
5
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
Piston
Cylinder Liner
Crankshaft
Slight taper
Notes on installing flywheel
Do not use a tool which
locks piston when
installing a flywheel, or
top of the piston may
be damaged. Also, do
not insert a screw
driver or the similar
into the exhaust port.
It is recommended to use Crankshaft
Clamp 1521 (Code No.71530200) available
as an optional tool.
It is made of durable engineering plastic
and locks the crankshaft without risk of
damage to any part of the engine.
When the engine is cold.
6
Application is as follows:
Remove the crankcase rear cover plate from the
engine and rotate the crankshaft to the bottom
dead center (BDC) position.
Insert the crankshaft clamp so that its grooved
portion surrounds the crankpin and lower end of
the connecting rod and securely tighten the fan
or clutch onto the crankshaft.
When the engine is hot.
BDC position
Rotate the crankshaft so that the
connecting rod comes to this position.
Insert this groove onto
the connecting rod.
7
NOTES WHEN APPL YING
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 pumped out fuel getting
into your eyes.
We do not recommend running your boat
NOTE
on the sea, or in any other saltwater
environment. Under such conditions, it is
difficult to prevent the engine from
becoming corroded and, eventually,
inoperative.
8
INSTRUCTIONS
The
MAX-
21VZ-M is designed expressly
for 21 class boat racing. P7 Turbo plug
is supplied with the engine and also
water cooled plug cap is installed,
which improves power output, fuel
consumption and durability. 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.
Standard accessories
Glow Plug P7 For T-type head
(Turbo head) 1piece
Cylinder-head gasket
(0.1mm) 1 sheet
Dust Cap 3, 16, 18
1piece each
(Medium Type)
Water Cooled Plug Cap
Flywheel No.2K Assembly
(Taper Collet,)
(Installed)
Exhaust Seal Ring 1piece
Head Gaskets
The engine is installed a 0.2mm thick head
gasket. If you find the following symptoms
after running the engine, add a 0.1mm thick
gasket supplied.
With the appropriate needle setting, engine
r.p.m. drop and power loses during running.
Glow plug burns out frequently.
Composition and proportion of lubricant in the
fuel may affect the symptoms.
9
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 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.
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.
10
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.
GLOWPLUG IGNITER
Commercialy available handy glowplug
heater in which the glowplug battery
and battery leads are integrated.
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 a
slight damage.
REMINDER!
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.
STARTER BELT
Necessary for starting the engine.
It is suggested to keep a starter rope as a
reserve.
ELECTRIC STARTER AND STARTER BATTERY
Use a 12-volt electric starter
with suitable battery for starting the engine.
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.
SUPER FILTER (L)
Fit a filter to the outlet tube of your
refuelling container to prevent entry of
foreign matter into the fuel tank.
TOOLS
HEX SCREWDRIVER
Necessary for engine installation.
1.5mm, 2mm, 2.5mm, 3mm
SCREWDRIVER
Necessary for carburetor adjustments.
No.1, No.2, etc
LONG SOCKET WRENCH WITH PLUG GRIP
Recommended for easy removal and
replacement of the angled and recessed
glowplug, the O.S.Long Socket Wrench
incorporates a special grip.
11
(Option)
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