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Top Products
Tractors,
Lawn
and
Garden
-
110
and
112
Electrical
System
40
SM-2059
-
(Apr-57)
19'1ition
System
10-3
SPARK PLUG ANAL
YSIS
Fig.
4-Normol
Operotion
A
spark
plug
with
brown
to
grayish-tan
de-
posits
and
slight
electrode
wear
is
normal,
and
inciicates
good
engine
adjustm
e
nts.
A
spark
plug
having
this
appearanc
e
may
be
cleaned,
regapped
and
reinstalled.
Fig.
5-0il
Fouling
Wet
oily
deposits
with
a
minor
degree
of
elec-
trode
wear
may
be
caused
by
oil
pumping
past
worn
rings
or
excessive
valve
stem
guide
clear-
ance.
I
'Break-in'
1 of a
new
or
recently
over-
hauled
engine
before
rings
are
fully
seated
may
also
result
in
this
condition.
Usually,
the
spark
plug
can
be
degreased,
cleaned
and
reinstalled.
Install
a
new
spark
plug'
if
carbon
deposit
is
more
than
that
shown.
Fig.
6-Corboll
Fouling
Dry.
fluffy,
black
carbon
deposits
may
result
from
over-rich
carburetor
adjustments.
A
clog-
ged
air
cleaner
can
re
s
trict
air
flow
to
the
car-
buretor
causing
rich
mixtures.
Poor
ignition
out-
put
(faulty
breaker
pOints.
weak
coil
or
conden-
ser)
can
reduce
voltage
and
cause
misfiring.
A
fouled
spark
plug
is
the
result,
not
the
cause
of
this
problem.
After
the
cause
has
been
elimi-
nated,
the
spark
plug
can
be
cleaned,
reg-apped
and
reinstalled.
Fig.
7-Deposit
Fouling
Red,
brown,
yellow
and
white
colored
coatin
gs
which
accumulate
on
the
insulator
are
by
-pro-
ducts
of
combustion
and
come
from
the
fuel
and
lubricating
oil,
both
of
which
today,
ge
ne
ra
ll
y
contain
additives.
Most
powdery
depOSits
have
no
adverse
affect
on
spark
plug
operation.
how-
ever,
they
can
cause
intermittent
missin
g
wlder
severe
operating
conditions,
rs
pecially
at
high
rpm
and
under
heavy
loads.
If
insulator
is
heavily
coated,
install
a
new
spark
plu[!;.
Litho
in
U.S.A.