O.S. Engines 91SX-H - Manual (Page 16)

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short and simple running-in procedure is required and
can be carried out with the engine installed in the
model. For the first few flights with a new engine i.e.
while the engine is being run-in set the needle-valve
for a slightly rich mixture not excessively rich as this
may result in poor throttle response and cause the
engine to stope. About 2 turn open from the nomal
setting will usually suffice.
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ADJUSTMENT
The following adjustments are approximately correct
when using a fuel containing 25% lubricant and 10-
30% nitromethane.
Bear in mind that fuels containing relatively large
percentages of power-boosting nitromethane operate
at richer mixture settings than are needed for mild
fuels and will, therefore, require the Needle Valve to
be readjusted accordingly. The type and percentage
of lubricant used is also a factor here, as noted later
in these instructions.
This carburetor is not fitted with a throttle
stop screw. Instead, idling speed is adjus-
ted by means of the throttle trim lever on
the transmitter.
NOTE:
If the throttle response is poor or the engine
stops due to a temporarily over-rich mixture im-
mediately after the engine is started, pinch the
fuel line for one or two seconds until the engine
r.p.m. increase and the engine runs steadily.
Reminder!
Never touch, or allow any object to
come into contact with, the rotating ro-
tor.
All internal-combustion engines benefit, to some
degree, from extra care when they are run for the first
few times known as running-in or breaking-in.
This is allows the working parts to mate together
under load at operating temperature.
However, because O.S. engines are made with the
aid of the finest modern precision machinely and from
the best and most suitable materrials, only a very
RUNNING-IN ("Breaking-in")
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