O.S. Engines 12XZ Speed Spec III - Manual (Page 2)

Outer Head
Crankcase
Mounting Lugs
Exhaust
Cover Plate
Carburetor
Type (12F2-B)
Crankshaft
BASIC ENGINE PARTS
Crankshaft Bearing (Front)
Metering Needle Throttle Stop
Screw
Needle Valve
Carburetor Reducer
Ball Link
Dust Cover
The Needle-Valve:
Four adjustable controls are provided on this
carburetor.
For adjusting air/fuel ratio (air-fuel mixture) at maximum
rpm (fully opened throttle).
The Throttle Stop Screw:
For setting the minimum idle speed:
For adjusting idle and acceleration feeling.
The Metering Needle:
NOTE: While the Mixture Control Valve and the
Metering Valve are set at the standard position
when the engine leaves the factory, readjustment
may be necessary, occasionally to allow for
changes in fuel formula and climatic conditions
Readjust the controls only when satisfactory
results cannot be obtained with the standard
positions following the instructions mentioned in
the “CARBURETOR ADJUSTMENT” section.
INSTALLATION OF THE CARBURETOR
As delivered, the engine has its carburetor lightly installed
in the intake boss. Secure it as follows.
ENGINE INSTALLATION
Make sure that the vehicle's engine mounting surfaces
are level and in the same plane. Poor installation may
cause distortion of the crankcase, bearings, etc.,
resulting in erratic running and loss of performance.
The recommended screws for securing the engine are
3mm or 4-40 steel Allen hexagon socket type. If existing
holes in the engine mount do not align perfectly with
engine mounting lugs, enlarge them slightly with a
needle-file so that screws are in alignment with the
mounting holes.
Chamfer inside edges of bearers.
Do not allow bottom
of crankcase to
touch chassis.
Running- in is a procedure for an engine to come
close to actual running conditions (fuel, r.p.m.,
engine temperature, etc.).
Excessively rich running and prolonged low speed
running should be avoided. Prolonged low speed
running and low temperature running may result
in the oil in the fuel becoming gelled and the
piston/liner becoming stuck together.
PRESSURIZED FUEL SYSTEM
It is recommended that a muffler pressurized fuel
feed system be used so that the fuel may be stably
fed to the carburetor.
The following procedure is suitable when a fuel
containing 20% nitro-methane is used.
STARTING THE ENGINE & RUNNING-IN ('Breaking-in)
Turn the needle-valve clockwise until it stops.
This is the fully closed position.
Do not force it to turn further.
Needle Valve
Open
(Counter-clockwise)
Close(Clockwise)
2.5 turns opened from the fully closed position.
Note:
Sketch shows the carburetor reducer removed.
Set the throttle opening a little
wider (approx. 1mm) than the
standard setting by adjusting
the Throttle Stop Screw.
approx 1mm
Attention:
It is vitally important to set the
throttle at the correct position
before starting the engine. If
the engine is allowed to run
with the throttle too far open
under ''no load'' conditions
(i.e. with the driving wheels not in contact with the
ground) it will rapidly over-heat and may be
seriously damaged.
Mixture Control Valve
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 screw
gently until it stops.
Rotate the retaining screw gently until it stops, then
tighten a further 120-180 , and no more.
Do not overtighten the screw as this will damage the
thermo insulator.
Tighten a further
120-180
Note
Be careful not to damage the O rings when
removing the carburetor retainer from the engine.
First, remove the Retaining screw, then pull out
each retainer. Do not push the retainers in or the O
rings will get damage.
Retaining
Screw
"O" Ring
"O" Ring
Approx 0.5mm
Mixture Control Valve
Carburetor Body
Flush with the carburetor body.
2.
1.
4.
3.
[Standard Position]
[Fully closed position]
Slide Valve Carburetor Body
CARBURETOR CONTROLS STANDARD POSITIONS
(POSITIONS WHEN THE ENGINE LEAVES THE FACTORY)
[Standard Position]
[Standard Position]
Set the carburetor controls at the standard positions
(positions when the engine leaves the factory.)
Switch the transmitter and make sure that each
linkage moves correctly.
Make sure rotating direction of the starter box is
correct (counter-clockwise seen from the front edge
of the crankshaft), and turn the engine with the
starter box to draw fuel into the engine.
Connect glowplug battery lead to heat the plug and
start the engine with the starter box.
When the engine does not start or stops right after
being started, try the followings.
5. When the engine starts, warm it up by repeatedly
increasing the rpm to medium speed and back
again to a fast idle with the mixture set very rich,
glowplug connected, and the driving wheels clear of
the ground. The rich mixture will provide adequate
lubrication and cooling, indicated by profuse
exhaust smoke.
6. When the engine is warmed up, disconnect the
glowplug battery and try running the car on the
track. If the engine stops soon after running at
around mid speed, the mixture is too rich. Close the
needle-valve 15°.
If the engine still stalls, close the metering needle
15°. Run the car on the track until one tank of fuel
has been consumed, then close the needle-valve
very little (within 10°).
INSTALLATION OF THE STANDARD ACCESSORIES
Warning!
Do not touch rotating parts, engine
and silencer when stopping the
engine as they become very hot,
and contact with them may result
in a serious burn.
To stop the engine, close the
throttle to idle speed and shut it off
completely with the trim lever on the
transmitter then cut off the fuel
supply by pinching the fuel delivery
tube to the carburetor.
Fuel
How to stop the engine
Note:
In the event of any major working parts (e.g.
piston/cylinder liner assembly) being replaced or
the fuel being changed, especially to high nitro
fuel, the complete running-in should be repeated.
7. Repeat this procedure (close needle-valve very little
after one tank of fuel has been consumed) until approx.
2 liters of fuel have been consumed, extending gradually
the full throttle running time at the straight. Carefully
observe the exhaust smoke.
Be sure to run the engine with visible white smoke at
all times. If the smoke is not visible, the needle-valve
is closed too far.
Now the RUNNING-IN (Breaking-in) is completed.
Pull out
Slide Valve
Carburetor Body
Metering Needle
Flush with the ball link body.
Ball Link
[Standard Position]
Installing the glow plug. Insert RP6 plug supplied into
heatsink-head carefully, making sure that it is not
cross-threaded before tightening firmly.
(All the O.S. T-Type plugs including the RP6 are not
supplied with a washer.)
Install the exhaust seal ring
supplied.
Exhaust
Seal Ring
Themo Insulator
Set the needle-valve approx. 2 turns open from the
fully closed position. Do not force the needlevalve to
turn beyond a lightly closed position.