O.S. Engines 25XZ 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.
Expressly for 1/8 off-road truck (Truggy)
racing competitions
1
2-5
6
7
8
14
15
19-23
27-29
24-26
30-33
9
16
34-35
17
18
10-12
13
CONTENTS
INSTALLATION OF THE CARBURETOR
ENGINE INSTALLATION
STARTING THE ENGINE &RUNNING-IN
("Breakinh-in")
FINAL ADJUSTMENT
CARE AND MAINTENANCE,
CHECKING THE ENGINE
TROUBLE SHOOTING
ENGINE EXPLODED VIEW & PARTS LIST
CARBURETOR EXPLODED VIEW &
PARTS LIST
O.S. GENUINE PARTS & ACCESSORIES
THREE VIEW DRAWING
36-37
SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR O.S. ENGINE
ENGINE CONSTRUCTION
NOTES WHEN APPLYING AN ELECTRIC
STARTER
NOTES ON OPERATION
ABOUT THE ENGINE
BEFORE STARTING
BASIC ENGINE PARTS
CARBURETOR CONTROLS
GLOWPLUG
INSTALLATION OF THE STANDARD
ACCESSORIES
38-39
40
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 an 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.
•
•
•
•
4
!
This engine is intended for model cars.
Do not attempt to use it for any other
purpose.
Mount the eng ine 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
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.
NOTES
•
•
•
•
•
•
5
!
NOTES
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 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.
•
Before starting the engine, always check
the tightness of all the screws and nuts
especially the mounting screws and
movable parts such as the throttle arm.
Missing retightening the loose screws
and nuts often causes the parts
breakage that is capable of harming you.
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 therefrom, in actual use.
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
NOTES ON OPERATION
9
Standard accessories
Glow Plug P3 T-type head (Turbo head)
1piece
Exhaust Seal Ring 1piece
Dust Cap 3, 16, 18 1piece each
The MAX-25XZ is a high performance .25
cu.in. class power unit for one-eight-scale
radio-controlled truck type (Truggy) cars.
It has been expressly designed for racing
competitions. It features a large size
outer head and T-type plug (turbo plug)
design.
The 21JN carburetor is supplied with
8mm reducers to manage different
course conditions.
(Hot Type)
ABOUT THE ENGINE
10
Tools, accessories, etc.The following items are
necessary for operating the engine.
T-2060 WN TUNED SILENCER ASSEMBLY
M2000 EXHAUST HEADER PIPE ASSEMBLY
T-2060SC WN TUNED SILENCER COMPLETE SET
SUPER AIR CLEANER 203 ASSEMBLY
BEFORE STARTING
Optional Extras
GLOW PLUG T-Type (Turbo Plug)
P3 is supplied with the engine. As
replacement, suggested O.S. plugs are
P3 and P4.
This is a heavy-duty wet type air cleaner
designed specifically for 3.5cc ‘off-road’ model
car engines.
This is designed to use with the T-2060
Tuned Silencer.
This is designed specifically for 3.5cc ‘off-road’
model car engines.
This is a set of T-2060SC Tuned Silencer and
M2000SC Exhaust Header Pipe Assembly.
T-2060SC WN TUNED SILENCER ASSEMBLY
M2000SC EXHAUST HEADER PIPE ASSEMBLY
This is designed to use with the T-2060SC
Tuned Silencer.
This is designed specifically for 3.5cc ‘off-road’
model car engines.
SUPER JOINT TUBE 21
28XZ HYPER FLYWHEEL SETS
They are designed to match the engine power
characteristics.
This is to use with joint tube connection type
silencer.
11
TOOLS
HEX SCREWDRIVER
SCREWDRIVER
Necessary for engine installation.
1.5mm, 2mm, 2.5mm
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.
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
!
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.
REMINDER!
12
FUEL FILTER
GLOWPLUG IGNITER
Commercialy available handy
glowplug heater in which the
glowplug battery and battery
leads are integrated.
To installed in the fuel line between
fuel tank and carburetor to prevent
foreign matter from entering the
carburetor.
FUEL PUMP
For filling the fuel tank, a simple,
polyethylene "squeeze" bottle,
with a suitable spout, is required.
STARTER BOX
For starting the engine.
SILICONE FUEL LINE
Heatproof silicone tubing of
approx. 5mm o.d. and 2mm i.d.
is required for the connection
between the fuel tank and
engine.
7.2V BATTERIES FOR STARTER BOX
Batteries for starter box.
Select according to the
starter box used. Be sure to
fully charge before using.
!
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.
13
Outer Head
Crankcase
Mounting Lugs
Exhaust
Cover Plate
Carburetor
Type 21JN
Crankshaft
BASIC ENGINE PARTS
Crankshaft Bearing (Front)
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