Ignition System
71
NOTE: Intermittent failure requires tests for voltage
and resistance to be made when the engine
is cold, and again when it is hot. Typical cus-
tomer complaint: “It stops after I mow for 10
minutes and I can’t get it to re-start”.
• To confirm that the problem is ignition-based, it
is necessary to “catch it in the act”.
• Resistance normally increases slightly as tem-
perature increases.
NOTE: Failure of the magnets in the flywheel is
exceedingly rare. To test the magnets, sim-
ply hold an item made of ferrous metal
roughly 1/4” (6.35 mm) away from the mag-
nets in the flywheel. It should be drawn to
the flywheel. A wrench or screwdriver is suit-
able for this test.
NOTE: An inexpensive compass or bar magnet can be used to confirm opposite polarity of the flywheel mag-
nets. See Figure 7.11.
7. Inspect the flywheel.
The flywheel is a frequently forgotten component of the ignition system. It holds the magnets that induce a field in
the module which in turn produces a spark. But it also controls the timing of the ignition system by controlling when
the magnets are introduced to the module.
A sheared flywheel key will throw off the ignition timing. To inspect the flywheel and key:
1. Remove the recoil assembly by following the steps describe in Chapter 6: Starter.
2. Remove the flywheel by following the steps described in the flywheel section of this chapter.
3. Inspect the flywheel key and the key way on the crank shaft.
NOTE: If the flywheel key is damaged, replace it. If the keyway on the crankshaft is damaged, the engine must
be short blocked.
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