O.S. Engines FS-120S III - Manual (Page 13)

Since the FS-120S 3 is intended to be started with an
electric starter, the addition of a spinner assembly for
centering the starter sleeve is desirable. Special propeller
locknut sets are available for use with spinners.
PROPELLER & SPINNER ATTACHMENT
Ream the propeller shaft hole to 8.0mm bore with an
appropriate reamer, checking that the hole is exactly
centered.
Fit the prop to the engine shaft, followed by the retaining
washer and prop nut and tighten firmly with a 14mm
wrench.
Reminders:
AII 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.
Though not as volatile as gasoline, model engine fuel is
also highly inflammable.
Keep it away from on open flame, excessive heat,
sources of sparks, or anything else that might ignite it.
Smoking is firmly discouraged.
There is a risk, particularly
with powerful four-stroke
engines, of the propeller flying
off if the prop nut loosens due
to detonation ("knocking") in
the combustion chamber when
the engine is operated too
lean, or under an excessively
heavy load.
Obviously, this can be very hazardous. To eliminate such
dangers, the O.S. Safety Locknut Assembly was devised. Fit
this as follows:
Lock Nut
Propeller Washer
Propeller Nut
1.
2.
3.
Two adjustable controls are provided on these carburettors.
They are as follows:
TYPE 70N 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 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 sequence in which these controls are adjusted is
explained in the succeeding sections, under Starting,
Running-in and Idling Adjustment.
•
•
Add the special tapered and slotted locknut and secure
with a 14mm wrench while holding the prop nut with the
17mm wrench.
Alternative Needle Valve
If it should be found(e.g. after a change of fuel or in operatibg
conditions) that the needle-valve appears to be unduly
sensitive, it may be preferable to replace the standard needle
with the less sharply tapered optional needle(Code
No.45581970) supplied as an accessory with this engine.
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