194
Two-Stroke Engines
Copyright Goodheart-Willcox Co., Inc.
down, or fouled completely. Measure and record
the spark plug gap. The spark plug gap is the dis-
tance between the spark plug center electrode
and the ground electrode. See Figure 9-22A.
Compare the measurement with the size of the
gap recommended by the engine’s manufac-
turer. Use a wire gauge, Figure 9-22B, to mea-
sure the gap correctly.
One or more of the engine covers will need to
be removed in order to inspect the ignition sys-
tem further. Typically, the rewind starter covers
the flywheel. Removing the cover should expose
the ignition coil. In Figure 9-23, the ignition
coil is visible. A connector connects the ground
wire to the ignition coil. The other end of the
ground wire is connected to the stop switch.
If the spark test failed earlier, the coil or
the stop switch could be bad. Disconnect the
ground wire from the ignition coil itself. With
the ground wire removed, the coil is isolated
from the stop switch. Place the wire where it
will not contact any engine metal. Figure 9-24
shows the ground wire disconnected from the
coil and twisted slightly so it would not con-
tact the coil’s kill tab when the rewind starter is
reinstalled. Reinstall the rewind starter. Attach
the spark tester to the spark plug and retest
for spark. If the coil produces a spark, the stop
switch is probably bad. If the coil does not pro-
duce a spark, the coil is probably bad. Remove
the rewind starter.
Test a toggle-type stop switch using a digi-
tal multimeter set to measure continuity. Make
sure the ground wire has been removed from the
ignition coil. Connect one of the meter leads to
Ground
electrode
Spark
plug gap
Wire gauge
A B
p ug gap
Center
electrode
Goodheart-Willcox Publisher
Figure 9-22. For the engine to run correctly, the spark plug gap should be within the specifications set
by the engine’s manufacturer. A—The spark plug gap is the measurement between the center electrode
and the ground electrode. B—A wire gauge is the correct tool to use to measure the gap.
Ignition coil
Ground wire
connected
Goodheart-Willcox Publisher
Figure 9-23.The engine cover(s) will need to be .
removed to provide access to the ignition coil and
flywheel.