RUNNING-IN (“Breaking-In”)
All internal-combustion engines benefit
from extra care when they are run for the
first few times known as running-in or
breaking-in.
This allows the working parts to mate together
under load at operating temperature.
Therefore, it is vitally important to complete the
break-in before allowing the engine to run
continuously at high speed and before
finalizing carburetor adjustments.
However, because O.S. engines are
produced with the aid of the finest modern
precision machinery and from the best and
most suitable materials, only a short and
simple running-in procedure is called for
and can be carried out with the engine installed in the model.

The process is as follows:

1. Install the engine with the propeller
intended for your model. Open the
needle valve to the advised starling
setting and start the engine. If the
engine stops when the glow plug
battery disconnected, open the needle
valve to the point where the engine
does not stop. Run the engine for one
minute with the throttle fully open, but
with the needle valve adjusted for rich,
slow "four-cycle" operation.

2. Now close the needle valve until the
engine speeds up to "two-cycle"
operation and allow it to run for about
10 seconds, then reopen the needlevalve
to bring the engine back to "four
cycle" operation and run it for another
10 seconds. Repeat this procedure
until the fuel tank is empty.

3. Re-start and adjust the needle-valve so
that the engine just breaks into "twocycle"
from "four-cycle" operation, then
make three or four flights, avoiding
successive "nose-up" flights.

4. During subsequent flights, the needle
valve can be gradually closed to give
more power. However, if the engine
shows signs of running too lean, the
next flight should be set rich. After a
total of ten to fifteen flights, the engine
should run continuously, on its
optimum needle-valve setting, without
loss of power as it warms up.

5. After the completion of the running-in
adjust the carburetor at optimum setting
referring to “MIXTURE CONTROL
VALVE ADJUSTMENT” section and
“SUBSEQUENT READJUSTMENT”
section.