O.S. Engines FS-120S-E - Manual (Page 7)

12
CARBURETTOR
The Needle Valve
This is used to establish the fuel/air mixture strength
required for full power when the throttle is fully open.
The Mixture Control Valve (Mixture Control Screw)
This is used to establish the mixture strength required for
steady idling and a smooth transition to medium speeds.
(The varying mixture strength required between part-throttle
and full-throttle running is automatically adjusted by coupled
movement of the throttle.)
The Throttle Stop Screw
For establishing the minimum idling speed.
The sequence in which these controls are adjusted is
explained in the succeeding sections, under Starting,
Running-in and Idling Adjustment.
•
•
Three adjustable controls are provided on this carburetor.
•
Needle Valve
Mixture Control Valve
(Mixture Control Screw)
Throttle Stop Screw
Rotor Guide Screw
Photo 2
Photo 3
STARTING
Be sure to use a high-torque electric starter.
Hand starting is very dangerous as this is a bug capacity
four stroke glow engine and sudden strong knocking may
occur with priming quantity, engine temperature, fuel used,
etc.
WARNING:
13
Use the choke valve only when the fuel does not comes to the
carburetor with above procedure.
Check that the current to the glowplug is switched off.
Check that the polarity of the starter battery leads rotates the
engine counter-clockwise when viewed from the front.
Open the needle-valve 2.5 turns when the muffler
pressurized is applied, or 3 turns when the muffler
pressurized is not applied from the fully closed position and
temporarily set the throttle in the fully open position.
Apply the starter and press the starter switch for 5-6
seconds, or until fuel is seen to emerge from the exhaust
outlet, indicating that the cylinder is now primed. Energize the glowplug and apply the starter. If the starter
fails to rotate the engine completely, this may be due to the
cylinder being over-primed, or to the starter battery being
insufficiently charged. 1.
2.
3.
4.
5.
6.
Check these conditions and, instead of pressing the starter
button after applying the starter, have the starter spinning
before applying it to the engine, to give it a "running start".
When the engine starts, slowly open the throttle, leaving
the needle-valve at its rich starting setting to promote cool
running conditions.
However, if the engine slows down because the mixture is
excessively rich, the needle-valve may be closed a little to
speed it up until it runs evenly.
Now disconnect current to the glowplug and gradually close
the needle-valve so that revolutions are increased. Make
adjustments to the needle in small steps. Abrupt changes
at this stage are likely to cause the engine to stall. Restart
the engine by simply applying the starter with the glowplug
re-energized and the throttle at its starting setting.
7.
8.
Disconnect the glowplug battery.
Close the choke valve.
Turn the propeller counter-clockwise slowly by hand until
the fuel reaches the carburetor.
Release the choke valve.
CAUTION:
9.
Excess quantity of fuel in the engine makes the engine start
difficult and may result in an hydraulic lock that may
damage the engine.
Close the throttle-arm to within 15-20 ° of the fully closed
position and slowly turn the prop "backwards" (clockwise)
by hand approximately 1.5 turns until it is arrested by
compression.This is to enable the kinetic energy of the prop
to subsequently assist the starter through the compression
stroke to start the engine.
CAUTION:
Regard the choke valve as a supplementary device to draw
the fuel to the carburetor. Do not apply an electric starter
with the choke valve closed or turn the propeller too much,
which may result in an hydranlic lock that damage the
engine. Apply an electric starter only after making sure that
no extraordinary stiffness is telt when rotating a propeller.
Do not use the choke valve to stop the engine which also
causes an hydraulic lock and damage the engine. Be sure
to disconnect the glowplug battery when rotating a
propeller by hand which may cause a heavy insure with
sudden and strong knocking.