Service Manual
Coil,
Ignition
Part Number
NN10730
Purpose
Provides voltage necessary to fire spark plug.
How
It
Works
Magnets on the flywheel passing by the primary windings in the coil
create a changing field around the coil to generate current. A second
coil, called the secondary, is also wound around the same iron core. This
second coil is used to “step up” the voltage. It uses smaller wire and
more windings to do this.
The two coils alone are not enough to produce the 20,000 volts
necessary to fire the plug. The trigger module is what actually does the
job. The electronic equivalent of points,
it
breaks the primary circuit just
as the magnets are passing by. This causes a VERY rapid change in the
field produced by the primary which results in the secondary producing
the necessary 20,000 volts.
Testing
1. Insure that the flywheel magnets are
OK.
2.
Insure that core of coil is well grounded.
3. Disconnect kill wire and attempt to start.* If spark is produced, coil is
OK.
4.
Resistance check: Check primary coil resistance by connecting VOM
leadsd to kill wire and iron core. Check secondary coil by connecting
between spark plug lead and core. See below for proper resistance.
Test
Reading
Primary Coil Resistance 1
.O
ohms
Secondary Coil Resistance
9.5K
ohms
*Note: Disconnecting the kill wire will defeat the safety circuit and the
key switch. Be sure that unit is in NEUTRAL and the PT0 is
OFF
before
starting. To turn off the engine, ground the kill wire.
Regulator,
Part Number
Voltage
N
N
10261
Purpose
Rectifies (changes AC current to DC) and regulates the output (limits the
voltage) of the alternator. Capacity:
20
amps.
How
It
Works
Rectification: The full wave current supplied by the alternator
is
pulsating current that never has a below zero value.
Regulation:As mentioned above, the DC provided by the rectifier pulses like
AC, but never goes below zero. The regulator takes advantage of the pulses
by ‘‘lopping’’ the top
off
the wave. The result is a lower average voltage.
Testing
1.
Insure that battery is fully charged and in good condition.
2.
Start the engine and measure the voltage at the battery terminals with
Regulator converted to full wave rectified by a bridge rectifier. The result is a
a voltmeter.
It
should read between 13.6 and 14.7 volts DC.
If Higher: Replace Regulator.
If
Lower: Check for proper ground connections, broken wires or
terminals, and/or blown fuses. Start engine and test
again. If still lower, check the alternator for proper output.
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