O.S. Engines FS-26S-CX - Manual (Page 11)

GLOWPLUG
The role of the glowplug
Glowplug life
Particularly in the case of very high performance
engines, glowplugs must be regarded as
expendable items.
Install a plug suitable for the engine.
Use fuel containing a moderate percentage of
nitromethane unless more is essential for
racing events.
Do not run the engine too lean and do not
leave the battery connected while adjusting the
needle.
However, plug life can be extended and engine
performance maintained by careful use, i.e.:
With a glowplug engine, ignition is initiated by
the application of a 1.5-volt power source. When
the battery is disconnected, the heat retained
within the combustion chamber remains
sufficient to keep the plug filament glowing,
thereby continuing to keep the engine running.
Ignition timing is 'automatic' : under reduced
load, allowing higher rpm, the plug becomes
hotter and, appropriately, fires the fuel/air charge
earlier; conversely, at reduced rpm, the plug
become cooler and ignition is retarded.
Apart from when actually burned out, a plug may
need to be replaced because it no longer
delivers its best performance, such as when:
When to replace the glowplug
The FS-26S-C and FS-26S-CX are supplied with
an O.S. Type F glowplug, specially designed for
O.S. four-stroke engines.
Filament surface has roughened and turned
white.
Filament coil has become distorted.
Foreign matter has adhered to filament or plug
body has corroded.
Engine tends to cut out when idling.
Starting qualities deteriorate.
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