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CHECKING THE SPARK
PLUGS
Remove the
spark
plugs and check their exterior. The appearance of elec-
trodes and insulators provides considerable information
on engine adjust-
ment and condition.
Electrodes and insulator
medium grey
-
good adjustment of carburetor and correct
performance of spark plug,
black -
mixture too rich,
light grey
-
mixture too lean,
oiled up -
misfiring or piston ring blow-by.
a
0.7mm .
.
028"
Clean the spark plugs with a brush and a chip of wood and blow them out.
The insulator should be clean and dry on the outside in order to avoid short
circuits or
tracking. Check
the electrode gap (0.7 mm.) and reset
if
neces-
sary by bending the outer electrode.
Use
a proper gasket when installing
the plug. Generally speaking you may count on a plug service life of up to
15.000 km. (10000 miles).
CHECK COMPRESSION
After warming up the engine,
remove
all 4 spark plugs. Operate the starter
motor with the accelerator pedal fully depressed
and
the throttle wide open.
The compression is checked by inserting an accurate compression
gauge
into each spark plug hole.
49
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