The plug should be cleaned on an abrasive blast machine and afterwards the
sparking surfaces of the electrodes on standard type plugs should be dressed with a
fine file in order to restore clean, flat, parallel faces. It is most important that the gap
should be re-set to specification, ·020—·025 ins. Gap adjustment should be made by
bending the side wire. The threads of the plug, and the gasket seat, should be wiped
clean before refitting the plug to the engine. The upper portion of the insulator
should also be wiped clean after fitting, and prior to connecting the H.T. cable. It is
good practice to wipe periodically the top of the insulator with a clean cloth in order
to remove any accumulation of grime or dust etc., as such deposits can be conductive,
and result in poor plug performance.
Fig. 3. The sparking plug
The special non-detachable steel gaskets fitted to Champion standard sparking
plugs are designed to last the life of the plug.
When refitting the plug, screw in as far as possible by hand, and then use a box
spanner for final tightening, to avoid possibility of damage to the insulator. An
adjustable spanner should not be used.
When refitting a plug make sure that the washer is not defective in any way.
Screw the plug down by hand as far as possible, then use a spanner for tightening
only. Always use a tubular box spanner to avoid possible fracture of the insulator,
and do not in any circumstances use an adjustable spanner.
Paint splashes, accumulation of grime and dust, etc., on the top half of the
insulator, are often responsible for poor plug performance. The plug should be wiped
clean frequently with a clean rag.
CARBURATION
The carburetter is of simple and robust construction and the only attention that may
be required is adjustment of the pilot jet and throttle stop.
An exploded view of the carburetter is shown in Fig. 4. Opening the twist grip
throttle control raises the throttle slide thus controlling the supply of air to the engine.
The tapered needle controlling the supply of fuel is attached to the throttle slide so
that a balanced mixture is always provided. The needle has five notches at its upper
end and it is secured in the throttle slide by the spring clip which locates in one of
these notches. The throttle valve size and the needle position are carefully set before
despatch from the factory and no alteration to these settings is necessary or desirable.
Mixture control at low speeds is by the pilot jet which has an adjustable air supply.
An adjustable throttle stop is also provided to regulate the slow running speed.
17
(Above)—Fouled
with burnt oil or soot
(Below)—Correct
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