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DDIIAAGGNNOOSSTTIICC TTEESSTTSS
TEST 33 - CHECK SPARK PLUGS
DISCUSSION:
During Test 32, if spark jumped the tester gap, the
ignition system must be functioning properly.
However, if the engine misses the spark plug itself
may be fouled.
PROCEDURE:
Remove spark plugs. Clean with a commercial sol-
vent. DO NOT BLAST CLEAN SPARK PLUGS.
Replace spark plugs if badly fouled, if ceramic is
cracked, or if badly worn or damaged. Set gap to
0.030 inch (0.76mm). Use a Champion RC12YC (or
equivalent) replacement spark plug.
Figure 7-35 – Setting Spark Plug Gap
RESULTS:
1. Clean and regap or replace sparks plug as necessary.
2. If spark plugs are good for gasoline models, go to Test 36. For
LPG models, go to Test 35.
TEST 34 - CHECK AND ADJUST IGNITION
MAGNETOS
DISCUSSION:
The ignition system used on GTV-760 engines is a
solid-state (breakerless) type. The system utilizes a
magnet on the engine flywheel to induce a relatively
low voltage into an ignition magneto assembly.
Ignition magneto internal components increase the
voltage and deliver the resulting high voltage across
the spark plug gap.
The ignition magneto houses a solid state-circuit
board that controls ignition timing. Timing is fixed and
spark advance is automatic.
Major components of the ignition system include (a)
two ignition magneto assemblies, (b) the spark plugs,
(c) the engine control board and (d) the engine fly-
wheel.
Solid-state components encapsulated in the ignition
magneto are not accessible and cannot be serviced.
If the magneto is defective, the entire assembly must
be replaced. The air gap between the magneto and
the flywheel magnet is between 0.012” to 0.015”.
The ignition magneto assembly (Figure 7-36) consists
of (a) ignition magneto, (b) spark plug high tension
lead and (c) spark plug boot.
Figure 7-36. – Ignition Magneto Assembly
In Test 32, a spark tester was used to check for
engine ignition. If sparking or weak spark occurred,
one possible cause might be the ignition magneto(s).
This test consists of adjusting the air gap between the
ignition magneto(s) and the flywheel. The flywheel
and flywheel key will also be checked during this test.
If no sparking occurs, the ground harness may be at
fault.
PROCEDURE:
1. Disconnect the J1 connector from the Engine Control Board.
Carefully remove Wire 18A from Pin Location J1-4. Connect
the J1 connector back to the engine control board. Repeat Test
32 “Check Ignition Spark”. If the unit now produces spark go to
Step 2. If the unit does not produce spark or has weak spark
go to Step 4.
2. Do the following:
a. Set a VOM to measure resistance. Connect
the positive (+) meter test lead to Wire
No.18A (Wire 18A still removed from the J1
connector) Connect the negative (-) meter
test lead to a clean frame ground. “Infinity”
should be measured, or 0.5 to 1M ohms,
depending upon the type of VOM used. If
“Continuity” is measured proceed to
Step12.
b. Set a VOM to the diode test range. Attach
the negative (-) meter test lead to Pin
Location J1-4 on the Engine Control Board.
(Wire 18A still removed from the J1 connec-
tor) Attach the positive (+) meter test lead
to frame ground. Set the Start-Stop Switch
to START. “Infinity” should be measure dur-
ing cranking and running. If the VOM does
not have a diode test range, set VOM to
measure resistance again. “Infinity” should
be measured.
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