Gravely 424 - Page 11

Z-
earbon
or
other
deposits.
This
can cause
the
high voltage
ignition
impulse
to
pass
from
the center
electrode
to
ground
without
jumping
the
spark
gap.
As
an
engine operates,
the
electrodes
are
gradually
buned or
worn
away.
In
time,
the
gapbecomes
so
wide
that
the
available
ignition
voltage
cannot
iump
the
gap
and
the
en$ne
misses.
Spark
plug
$ewicer
Every
100
hours removs
plug, check
cordition
and reset
gap.
Good operating conditions
are
iridicated
if
pt.rg has
light
coating
or
gray or tan
deposit.
A dead
white, blistered coating could
indicate
over-
heating.
e
bjac[
(carbon) coatiag
may
indicate
an
*over:ich"
fuel mixture caused
by clogged
air cleaner
or im-
propeicarburetor
adiustment.
Do not
sandblast,
wire
brush,
scrape or
otherwise
service
plug
in
poor
condition
-bert
results
are obiained
with
new
plug.
Set
spark
gap at.a25".
Tighten
plug
to
324
in.
lbs.
(27
ft.
lbs.) torque
when
installing.
BNEAKER
POINTS
Engine
operation
is
greatly
afiected
by
breaker
point
condition
and
adjustment of the
gap
If
points are
brrrnedl
badtly
oxidized,
Iittle
or no curreat
will
pass and-
as a result the engine
may not
operate
at all, or
if it
does
run
it
is likely
to
miss
particularly
at ful1 throttle.
Adjusting
breaker
point gap
affeets the
time that
the
con-
tacts
are opened
and elosed.
If
the
points
are
adiusted
to
-a
wider
gap,
they
will open
earlier and
close
later
in
terms
of cam
movement.
A deinite
time is
required
Jor
the
magnetic
ffeld within the
ignition coil
to
build
up
to
suffcient
value.
If the
cgntact
points are cloied
for
too
short a
time, a weak spark
will be
produced
by
the
coil.
If
points are
set too
wide,
they
will open
before
the
primary
curreat
reaches the maximum
value and
on
the
other
hand if set
too
close,
they
will open
after
the
primary
current
has
passed
its maximum
value.
Always
replace
badly
burned
or
pitted
breaker
points.
A
certain
amount of build-up
or mental
transfer
oc'
"urs
under
oot**l
operating
cronditions;
however,
if'this
occurs
too frequently
and becomes
excessive,
the
con-
denser
may
be at
faullt.
Shg[tly
pitted
points
can
be &essed
down
with a
point
ffle, although
this
shou]d
be
done
only
as
a temporary
field
ffx since
points
may
tend
to ar9
more
readily after ftling. Replace
points
at
ffrst
opportun'
ity
after
fflini.
ff
tire
points are
oiidized,
rub
a
piece of course
cloth
between the
srrfaees.
Dirty or
oily
points
cal
be
cleaned
with cloth
but make
sure
no
particles oI
lint are left between
surfaces.
CONDENSEN
If the condenser
shorts
out,
the
coil
will
be unable
to
product
output
voltage. On
the other
hand,
if
it
opens
or
decreases
in capacitance,
the output
voltage
will be
greatly
reduced
and the
ignition
points will burn
exces-
sively.
If
badly buined
breaker
points
occur
too frequeltly,
the condition
of
the condenser
should
be
suspected.
If condenser
iras too small
capacitane,
metal
will
transfer
from
the stationary
coatact
to
the movable
contact.
1f its
capacitance
is
too
large,
the
metal
will
build
up on
the stationary
eontact,
BUILD
UP ON
MOVASIE
CONlACT
SUILD UP ON
STAT I ONARY
CONTACT
COULD
INDICATE
COULD
INDICATE
OVER CAPACITANCE
I TANCE
Figure
5
-
Metol
Trqnsfer
-
3reqker
Points
IO
I'IOVABLI
CONTACT