Idle Mixture Adjustment; Valve Adjusting - O.S. engine fs-70II Owner's Instruction Manual

1.
Start and adjust the engine as detailed in the starting
instructions.
2. Now open the throttle fully and run the engine for no more
than 5 seconds with the needle-valve tuned to produce near
maximum r.p.m., then, immediately, slow the engine down
again by opening the needle-valve approximately one turn.
The rich mixture, so induced, will cool the engine, at the
same time providing increased of lubrication.
3. Allow the engine to run like this for about 10 seconds, then
close the needle-valve again to speed it up to near
maximum rpm for another 5 seconds.
4.
Repeat this process, alternately running the engine fast and
slow by means of the needle-valve, while keeping the
throttle fully open, then begin to extend the short periods of
high-speed operation until two full tanks of fuel have been
consumed.
WARNING:
When ground running the engine, avoid dusty or sandy
locations. If dust or grit is drawn into the engine, this
can have a ruinous effect, drastically shortening
engine life in a matter of minutes.
Following the initial running-in session, check for any
5.
looseness in the installation due to vibration, then allow the
engine a period of moderately rich operation in flight.
6. For the first flight, have the needle-valve set on the rich
side and adjust the throttle trim on the transmitter so that
the engine does not stop when the throttle is closed to the
idle setting.

IDLE MIXTURE ADJUSTMENT

Start the engine, open the throttle fully and set the needle-
1.
valve slightly rich (30-45°) from the highest r.p.m. setting.
2. Close the throttle to the idle position. Allow the engine to
idle for about 5 seconds, then reopen the throttle. The
engine should accelerate smoothly back to full speed.
If, instead, the engine responds sluggishly and emits an
3.
excess of white smoke from the exhaust, the idle mixture is
too rich. Turn the mixture control screw approx. 45°
clockwise to lean the idling mixture.
On the other hand, if the engine hesitates before picking up
4.
speed or even ceases firing completely, the idle mixture is
likely to be too lean. Turn the mixture control valve 90°
counter-clockwise to substantially enrich the mixture, then
back again 45° clockwise.
In paragraphs 3 and 4 above, the 45° total movements are,
5.
of course, approximate. It will be necessary to fine-tune the
mixture control screw 10-15° at a time to reach the best
setting for optimum throttle response.
6. Continue re-checking the idle mixture setting until the
engine responds smoothly and positively to operation of
the throttle at all times.
7. With each successive flight, close the needle-valve very
slightly until, at the end of about 10 flights, the needle is set
for full power. Do not "over-lean" the mixture in an attempt
to extract more power.
RUNNING-IN (continued)
If overheating should be suspected at any time during flight
8.
(i.e.if the engine begins to "labor") reduce power by partially
closing the throttle and land the aircraft to enable the
needle-valve to be readjusted to a richer setting.
Note:
Remember that, when the engine is not yet fully run-in,
the carburettor cannot be expected to give its best
response in flight. Abrupt operation of the throttle, for
example, may cause the engine to stall. Therefore, at this
time ,the aircraft should, as far as is possible, be flown at
an altitude sufficient to enable an emergency landing to
be safely made if the engine stops.
Once the engine has demonstrated that it can be safely
9.
operated at full power, the carburettor can be adjusted for
optimum throttle response, following the instructions given
in the next section.
14
Resetting of Mixture Control Screw
In the course of making readjustments, it is just possible that
the mixture control screw may be inadvertently screwed in or
out too far and thereby moved beyond its effective range.
The factory setting can be re-established as follows:
Set the throttle at the fully closed position.
Now carefully rotate the mixture control screw clockwise until
it stops. Finally, turn the mixture control screw back exactly
3turns for the FS-70SⅡ, 2 1/2 turns for the FS-91SⅡand 2
turns for the FS-91SⅡ-P.

VALVE ADJUSTING

ALL O.S. four-stroke engines have their valve(tappet)
clearances correctly set before they leave the factory. However,
if, after many hours of running time have been logged, a loss of
power is detected, or if the engine has to be disassembled or
repaired as a result of an accident, valve clearances should be
checked and readjusted, as necessary. O.S. Valve Adjusting
Tool Kit is available as optional accessory.
The kit comes in a plastic case and includes:
(Code No.72200060)
Feeler gauge 0.04mm
Feeler gauge 0.1mm
Hex. key 1.5mm
Wrench 5mm
15