LUBRICATION,
!\
'IAINTENANCE AND TUI\'E-UP
6.
important as the difference between the readings.
The recommended standard and
service limit cylin-
der compression pressures arc listed
in
Ta
bl
e
6.
Greater differences than Ihat listed
in
Ta
ble 6 indi·
calc broken rings, leaky or sticking valves. a blown
head gasket or a combination
of
all.
I
f a low reading (I
()O
0 or more) is obtained.
it
in-
dicates valve or ring Irouble.
To
detennine which.
pour about a teaspoon
of
engine oil through the
spark plug
hole onto the top
of
the piston. Tum
Ihe
engine over once
to
di
stribute the oil. then take an-
olher compression
te
st and record the reading. If
the
compression increases significantl
y.
the valves are
good
but
Ihe
ri
n
gs
;Ire
defecti
ve.
If the compression
does not
increase,
Ihe
v:llves require servicing. A
valvc(s) could
be
hanging open.
but
not burned. or a
piece
of
c:lrbon could
be
on II v:llve se
al.
Spark
Plug Selection
Spark
plugs arc available
in
va
ri
ous heat ranges.
hotter
or
colder than plugs origina
ll
y installed at
the factory.
Select a plug
of
the heat range designed for the
loads and temperature conditions under which the
bike will be run. The use
of
incorrect heat ranges
can cause a seized piston,
scored cylinder wall or
damaged piston crown.
In
ge
neral. use a
hOI
plug
fo
r low speeds. low
engine loads and low temperatures.
Use
a cold plug
f
or
high speeds, high engine loads and high
temperatures. The plug should operate hot enough
to
bu
rn off unwanted deposits, but
nOI
so hot that
it
is
damaged
or
causes preignition. A spark plug
of
the correct heat range will show a light tan col-
or
on
the portion
of
the insulator within the cylin-
der after the plug has been
in
service.
The reach (length)
of
a spark plug (Fi
gure
111
)
is also imporlant. A longer than normal plug could
interfere with the valves and pistons. causing
pe
rmanent and severe damage. The recommended
spark plug heat ranges arc listed
in
Table 6.
Spa
rk Plug Rcmo\'aI/Cl
en
ning
1.
Remove the
fu
el
tank
as
described in Chapter
Seven.
2.
Rem
ove
the bolt and cap nut securing the cyl·
indcr head left-hand cover (
figure
91).
Rem
ove
the
cover and rubber cushions.
CAUTION
If
any dirt falls illlo Iht'
c)'/imJu
II'ht'n
Ihe plug is remo\·ed.
seriOIiS
engi"e
damage
COliltl
occ
llr
.
3.
Use compressed air and blow away
any
dirt that
ma
y have passed
by
the rubber boot on the spark
plug lead and accumulated
in
the spark plug well.
4. Remove the spark plug with
an
17
mm spark
plug wrench.
NOTE
If plllg is difficult
to
remO\·e.
apply
penetrating oi/aro/Illd base ofplllg alld
leI it soak ill abol/t /0·20 mill/lies.
5.
Inspect the spark plug carefully. Look for a bro-
ken
ce
nt
er porcelain. excessively eroded electrodes
and excessive carbon
or
oil
fou
ling. Replace such
a plug.
If deposits arc
li
ght. the plug
may
be
cleaned
in
solvcnt with a wire brush or in a special
spark plug sandbla
st
cleaner. Regap
th
e plug as
explained
in
this chapler.
Spark
Plug
Gapp
ing and Insta
ll
ation
A
new
plug should
be
carefully gapped to ensure
a reliabl
e.
consistent spark.
You
must usc a special
spark plug gapping tool with a wire feeler gauge.
1.
Remove
Ih
e new plug from the box. Do
1I0t
sc
rew on the small piece (I.jgure
112
) that
is
sometimes loose
in
the box.
it
is
not
to
be
used.
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