O.S. Engines 120AX - Manual (Page 7)

12
8mm
TOOLS
HEX Screwdriver
SCREWDRIVER
Necessary for engine installation.
1.5mm, 2mm, 2.5mm, 3mm
Necessary for carburetor adjustments.
No.1, No.2, etc
Phillips Screwdriver
No.1, No.2, etc.
Socket Screwdriver
5.5mm, 7mm, 8mm
LONG SOCKET WRENCH WITH PLUG GRIP
Recommended for easy removal and
replacement of the angled and recessed
glowplug, the O.S.Long Socket Wrench
incorporates a special grip.
End Wrenches
8mm, 12mm, 14mm, etc.
Needle Nose Pliers
13
The role of the glowplug
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.
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.:
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
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.
Glowplug life
Particularly in the case of very high performance
engines, glowplugs must be regarded as expendable
items.
Since the glowplug and fuel combination used
may have a marked effect on performance and
reliability, it would be worthwhile to experiment
with different plug types. An O.S. No.8 glow-
plug is supplied with the engine.
Recommended O.S. plugs are the No.8 and A5.
Carefully install plug finger-tight, before final
tightening with the correct size plug wrench.
GLOWPLUG