16
GLOWPLUG
The role of the glowplug
Glowplug life
Particularly in the case of very high performance engines,
glowplugs must be regarded as expendable items. However,
plug life can be extended and engine performance maintained
by careful use, i.e.:
Install a plug suitable for the engine.
Use fuel containing a moderate percentage of
nitromethane.
Do not run the engine too lean and do not leave the
battery connected while adjusting the needle.
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
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.
Since the compatibility of the glowplug and
fuel may have a marked effect on
performance and reliability, it is suggested
to use the O.S. Type F plug when it is
necessary to replace. Carefully install plug
finger-tight, before final tightening with the
correct size plug wrench.
17
The Needle Valve
When set to produce maximum power at full throttle, this
establishes the basic fuel/air mixture strength. The correct
mixture is then maintained by the carburetor's built-in
automatic mixture control system to cover the engine's
requirements at reduced throttle settings.
The Mixture Control Valve
This meters fuel flow at part-throttle and idling speeds to
ensure reliable operation as the throttle is opened and
closed. The Mixture Control Valve is factory set for the
approximate best result. First run the engine as received and
readjust the Mixture Control Screw only if necessary.
Two mixture controls are provided on this
Carburetor.
Needle Valve
Mixture Control Valve
Throttle Lever
Fuel Inlet
Rotor Guide Screw
MIXTURE CONTROLS
The sequence in which these controls are adjusted is
explained in the succeeding sections, under Starting,
Running-in and Idling Adjustment.
CARBURETOR CARE & MAINTENANCE
If you experience difficulty in achieving consistent mixture
setting it could be due to foreign debris in the carburetor.
Carefully disassemble the carburetor and wash in methanol.
Do not use gasoline or kerosene that can effect the silicone
rubber "O" rings.
Debris tends to accumulate in
this area
Carburetor Parts Name
Breather
Inlet Nipple
