means
of
the spark, the fuel ignites and gives
the
engine movement.
Because
of
the
hostile environment in
which it works (constant
changes
of revolu-
tions, frequency
of
flying sparks, fuel with
oil impurities, etc.), the same performance
should not be
expected
from the spark plugs
as they
would
give
in an automobile. For these
reasons, a
periodic
cleaning
of
the spark
plugs
is necessary,
since
the acumulation of
cinder
on their electrodes can prevent the
jumping
of
the spark,
stopping
the engine
immediately. For this reason
we
recommend
that the rider a!ways
carry
a replacement
spark
plug, even
though
most
of
the
time it
will be possible to clean
off
the
cinder
for
the
spark plug
to
be
in
working
conditio
n
again.
Given the extremely
important
role of the
spark plugs, it is vital
to
choose
the exact
spark plug suitable in
thermic
nature and
size. This will
depend
on
the type of
work
to
which
the
motorcycle
is submitted, the ter-
rain where it is ridden, and the climate where
it 0perates, but the size of the spark plug
should be
of
the
dimensions
suitable to the
cylinder
head:
Moto
Matic
Calibration
Champion
L-85
0.4
to
0.5 mm
Since if a shorter
spark
plug is used (figure
No. 3):
A) The
volume
of
the
combustion
cham-
ber
increases, therefore the compression
ratio
goes
down
, causing the engine to
lo
se
power.
B) The spark
plug
spark
jumps
outside
the
point
of
the
combustion
chamber
where
firing is
most
efficient, thus increasing the
possibi
li
ty of failures, irregular running, and
wasting of fuel.
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