O.S. Engines FS-26S-CX - Manual (Page 14)

In the interests of a long working life and high
performance, every internal-combustion engine
needs to be "run-in" (or "broken-in" as the
procedure is also known). This means giving the
engine extra care and attention during the first
hour or so of its operational life. New parts need
to become "bedded-in", i.e. smoothed and
aligned to reduce friction and avoid distortion.
For this to take place, the engine must not be
overloaded or run too fast. The essential
ingredients here, are ample lubrication and
cooling. Such a condition is achieved by having
the engine operate on an extremely rich needle-
valve setting : the excess oil not only provides an
abundance of lubrication; it also conducts away
heat from the surrounding metal and this is
further assisted by the partial evaporation of the
alcohol content of the fuel.
STARTING, RUNNING AND ADJUSTMENT
With an aircraft engine, cooling is also aided, in
large measure, by the slipstream and some
model car enthusiasts elect to carry out initial
running-in, in this way by bench-mounting the
engine and temporarily fitting it with an aircraft
type drive hub and propeller. In the case of the
O.S. FS-26S-C, however, the fact that it is a four-
stroke engine with inlet pipe and carburettor
mounted high on the cylinder-head, means that
each charge of rich, cooling, fuel-air mixture is
admitted directly into the cylinder, instead of
being pre-heated in a lengthy journey via the
crankcase, as in the usual two-stroke model car
unit. With extra care, the FS-26S-C can,
therefore, be run-in ready-installed in the car.
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