3.
To measure resistance in the primary circuit,
connect one ohmmeter lead to the positive
(+)
terminal and the other to the negative
(-)
terminal
on the coil. The resistance should be between
3.87
and
4.73
ohms.
A
high resistance value indi-
cates an open circuit or poor connection inside
the coil, and the coil should be replaced.
4.
To
measure resistance in the secondary circuit,
connect the ohmmeter leads to the two high ten-
sion terminals (see Figure
6-8).
The resistance
measured should be between
12,600
and 15,400
ohms.
A
lower resistance value indicates a
shorted secondary winding.
A
high resistance
value indicates the coil has excessive internal
resistance or an open circuit. Replace coil if not
within specifications.
-
OHMMETER
-
OHMMETER
Chipped Insulator
-
Check for advanced timing.
Bend only side electrode when setting gap.
Splash Fouled
-
Check for accumulated com-
bustion chamber deposits. See Cylinder Head in
Section
6.
LightTan or Grey Deposits- Normal plug color.
Replace spark plugs that show signs of fouling for
electrode erosion, with spark plugs of the recom-
mended type. See Figure
6-9
on
recommended
method of checking plug gap.
ES-1374
FIGURE
6-9.
CHECKING PLUG GAP
Wiring
Ignition system wiring includes (1) One positive
(e+)
wire which carries the low voltage current from the
battery to the primary winding of the coil.
(2)
One
negative
(-)
wire which carries low voltage to the
points and condenser.
(3)
Two high tension wires
that carry the high voltage current from the secon-
dary winding of the coil to the spark plugs. The spark
plugs and coil secondary are all grounded to the
ES-1373
FIGURE
6-8.
TESTING COIL SECONDARY
enghe making a completecircuit foFthevoltage back
to the battery. The ignition coil primary (low voltage
Spark
Plugs
recommended in the Operators Manual.
A
careful
Remove
and
inspect
the
spark Plugs
at
the
intervals
side) is grounded when the breaker points close.
examination of the plug can often pinpointthesource
of an engine problem. The following covers some
common
spark
plug
conditions
and
the
probable
cause.
One Plug Carbon Fouled
-
Check for an open
Check
all
low
voltage
wiring
for
loose
connections
and cuts or breaks in the insulation. Clean all termi-
nals and connections and test for continuity with an
ohmmeter. Use a megger
to
check for breaks in the
spark plug wire insulation.
ignition cable or low compression.
Black Soot Deposits
-
Check for faulty choke
operation, overly rich fuel mixture, or dirty air
filter.
Oil Fouled
-
Check for faulty crankcase
breather, worn rings, or worn valve guides.
Burned or Overheated
-
Check for leaking
intake manifold gaskets, lean fuel mixture, or
incorrect ignition timing. Be sure plug is not in
-
wrong heat range.
CRANKCASE VENTILATION SYSTEM
The crankcase breather prevents pressure from
building up in the crankcase. It also prevents oil con-
tamination by removing moisture or gasoline vapors
and other harmful blow-by materials from the crank-
case. These vapors are routed to the carburetor
where they are mixed with incoming airand burned in
the combustion chamber.
A
sticky breather valve can
cause oil leaks, high oil compression, rough idle,
reduced engine power and a rapid formation of
sludge and varnish within the engine.
6-1
0
Redistribution or publication of this document
by any means, is strictly prohibited.
Redistribution or publication of this document
by any means, is strictly prohibited.
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