Icnition
Sptem
Ovcrhc
Jtmg
Norm
Jl
i
r
rJ
I
ttr
I
i
V
Carbon
fould
Fig
85
Spark
plug
Life
plug
heat
range
Carbon
fouled
Dry
fluffy
carbon
depo
lts
on
the
Insulator
and
electrode
were
mostly
caused
by
slow
speed
dnvlng
In
cIty
weak
Ig
nltlOn
too
nch
fuel
mixture
dirty
aIr
cleaner
etc
It
IS
advIsable
to
replace
WIth
plugs
havmg
hotter
heat
range
011
fouled
Wet
black
depoSits
show
excesSive
oIl
entrance
Into
combusllon
chamber
through
worn
rmgs
and
pIstons
or
excessIve
clearance
between
valve
gUIdes
and
stems
If
the
same
condition
remams
after
repair
use
a
hotter
plug
Overheatmg
WhIte
or
hght
gray
msulator
WIth
black
or
gray
brown
spots
and
blUIsh
burnt
electrodes
indIcate
engme
overheatIng
Moreover
th
e
appearance
results
from
in
correct
IgnitIon
tIming
loose
spark
plugs
low
guel
pump
pressure
wrong
selectIOn
of
fuel
a
hotter
plug
etc
It
IS
adVisable
to
replace
WIth
plugs
havmg
colder
heat
range
After
cleaning
dress
electrodes
With
a
small
fine
file
to
flatten
the
surfaces
of
both
center
and
Side
electrodes
In
parallel
Set
spark
plug
gap
to
specification
FIg
86
Settmg
spark
plug
gap
Install
spark
plugs
and
torque
each
plug
to
11
to
15
ft
Ib
Connect
spark
plug
wires
Cleaning
and
Regap
Clean
spark
plugs
In
a
sand
blast
type
cleaner
A
VOId
excessIve
blasting
Clean
and
remove
carbon
or
OXide
depoSits
but
do
not
wear
away
porcelain
If
depos1ts
are
too
stub
born
discard
plugs
After
cleaning
spark
plugs
renew
firing
sur
face
of
electrodes
With
file
mentioned
above
Then
gap
spark
plugs
to
0
030
to
0
035
In
uSing
a
round
wire
feeler
gauge
All
spark
plugs
new
or
used
should
have
the
gap
checked
and
reset
by
bending
ground
electrode
II
