Ignition Troubleshooting
WARNING
DANGER - HIGH VOLTAGE/SHOCK HAZARD! Do Not touch ignition components
and/or metal test probes while engine is running and/or “cranked.”
Test Sequence
1-A. Check primary input voltage to coils. (See Test Chart, following)51843
1. If voltage readings to coil(s) are BELOW specification, proceed with Step 2-A.
2. If voltage readings to coil(s) are WITHIN specification, proceed with Step 1-B.
1-B. Check coils for spark. [Connect Spark Gap Tester (91-850439)].
1. If no spark or weak spark, COIL is bad.
2. If spark is OK, proceed with Step 1-C.
1-C. If Steps 1-A and 1-B check OK, replace spark plugs.
If problem still is evident after replacing spark plugs, proceed with Step 1-D.
1-D. If Steps 1-A, 1-B and 1-C check OK, check ignition timing.
1. If ignition timing DOES NOT check to specification (sudden and unexplained timing
change), check trigger advance linkage for loose or broken parts and check trigger magnet
ring in flywheel (affixed to flywheel hub) for tightness and/or shift in position.
2. If ignition timing is UNSTABLE (timing jumps around, at “cranking” speed and/or low
RPM), proceed to Step 5-A.
3. If ignition timing checks to specification and engine still does not run or runs poorly,
trouble exists with fuel system or engine mechanical.
2-A. Check switch box “stop” circuit. (See Test Chart, following.)
1. If reading is BELOW specification, proceed with Step 2-B.
2. If reading is ABOVE specification, either the trigger or switch box is bad (test trigger: if
trigger checks to specification replace switch box and repeat check).
3. If reading is WITHIN specification, proceed with Step 3-A.
2-B. Check ignition switch/wiring, as follows:
WARNING
DANGER--HIGH VOLTAGE SHOCK/FIRE HAZARD. STAY CLEAR OF SPARK PLUG
LEADS. To assure personal safety, each individual spark plug lead should be
grounded to the engine.
1. To prevent engine from starting, remove spark plug leads from ALL spark plugs, then
ground ALL spark plug leads to the engine.
2. Remove ignition switch lead wire(s) from switch box(es) [lead wire(s) are connected
to BLACK/YELLOW bullet terminal].
NOTE: Be sure to disconnect ignition switch lead wire from both switch boxes.
3. With ignition switch ISOLATED (removed in preceding Step 2), repeat check in Step 2-A.
a. If reading still is BELOW specification, proceed with Step 3-A.
b. If reading now is WITHIN specification, either the ignition switch or wiring is bad.
3-A. Check stator low speed and high speed input to switch box. (See Test Chart, following.)NOTE: This is OUTER switch box.
1. If either the low speed or high speed reading to switch box is BELOW specification, stator
or switch box is bad (test stator: if stator checks to specification replace switch box
and repeat check).
2. If both the low speed and high speed readings are WITHIN specification, proceed with
Step 4-A.
4-A. Check stator low speed and high speed input to INNER switch box. (See Test
Chart, following.)
1. If either the low speed or high speed reading to switch box is BELOW specification stator
or switch box is bad (test stator: if stator checks to specification replace switch box and
repeat check)
2. If both the low speed and high speed readings are WITHIN specification, proceed with
Step 5-A.
5-A. Check switch box bias. Bias circuit may checked using either a voltmeter or an
ohmmeter. (To use a voltmeter, see Test Chart, following. Use VOLT METER only; DVA
not required.
Ohm Test:
1. Disconnect WHITE/BLACK wire from switch box at bullet connector.
2. With ohmmeter set to 1K scale, connect one ohm lead to WHT/BLK switch box terminal
and one ohm lead to switch box case ground.
3. Ohmmeter should indicate 1300 - 1500 ohms.
Voltage TestNOTE: Switch Box Bias Voltage is NEGATIVE (-) voltage applied to the ignition system to
raise the trigger firing threshold as engine RPM is increased, thus stabilizing ignition timing
and preventing random ignition firing.
4. If bias reading is BELOW specification, one or both switch boxes are bad.
Replace OUTER switch box and recheck bias; if necessary, replace INNER switch box and
recheck bias.
5. If bias reading is WITHIN specification, and engine still does not run or runs poorly, one
or both switch boxes or trigger is bad. [Test trigger: if trigger checks to specification replace
switch box(es) and repeat check.]
Ignition System Test Chart
IMPORTANT: BEFORE attempting the ignition system checks, below, thoroughly
read the preceding pages of these instructions to become familiar with the proper
test sequence and procedures (particularly any “Warnings” and “Cautions”). ALL
tests are performed with lead wires connected--terminals exposed. SWITCH BOXES
MUST BE GROUNDED (CASE TO ENGINE BLOCK) FOR ALL TESTS--IF NOT, SWITCH
BOXES MAY BE DAMAGED.
(1) Using meter only, REVERSE LEAD POLARITY; Connect leads as specified.
(*) If using a meter with a built-in DVA, place selector switch in the DVA/400 VDC position.
Maybe you already have this information? But if not, keep the multimeter handy!
Good luck with resolving your spark issue...hope you find it before the party!
