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Introduction
Engine
10
1.5 SPARK PLUGS
1.
Insulator
2.
Body
3.
Gasket
4.
Electrode
5.
Earth electrode
6.
Threads
SPARK PLUG CHECK
1,000 km
• Remove the spark plug while the engine is hot ( taking utmost care to avoid
scalding!).
• The carbon deposits and the colour of the insulator ( around the central
electrode) provide good information as to the heat range of the spark plug
and to carburetion, lubrication and general condition of the engine.
• A light brown colour of the insulator indicates that engine working conditio-
ns are generally correct.
• Sooty black deposits, that are dry ( to the touch) and opaque, are a sign that
working temperature is too low, i.e. that the heat range of the spark plug is
too high, mixture too rich or ignition defective.
•A whitish colour of the insulator is indicative of too lean a mixture or of too
low a heat range of the spark plug (i.e. spark plug too “hot”).
• Check electrode gap (F-6) (even if the spark plug is new) by means of a
calibrated thickness gauge. If necessary, adjust by acting only on the earth
electrode.
F-5
F-6
Pr Tr - Nm
20 - 25
