A light deposit due to any of these causes can easily be cleaned off, but if it is
allowed to accumulate, particularly inside the body, the plug may spark internally
with an adverse effect on engine performance—if, indeed, it does not stop the engine
altogether. The plug should be cleaned and tested at regular intervals, and it is
suggested that this service be performed at your garage on a special “air blast”
service unit. If eventually the cleaning process fails to restore the plug to its original
condition of efficiency, it should be replaced by a new one.
When inspecting a plug, also check the gap between the points. This should be
.018—.020 in. (.44—.50 mm.) and adjustment should be made by bending the side
wire (Fig. 5). N
EVER ATTEMPT TO MOVE THE CENTRE ELECTRODE
, and it is always
advisable to use the special plug gap tool illustrated, obtainable at 2/- from any
Champion Plug stockist or from the Champion Sparking Plug Co. Ltd., Feltham,
Middlesex. Feeler gauges are attached to verify correct gap.
When refitting a plug make sure that the copper washer is not defective in any
way. If it has become worn and flattened, fit a new one to ensure obtaining a gas-
tight joint.
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.
16
F
IG
. 6.
The carburetter.
