1. Using a multimeter:
a. Remove the spark plug wire from the spark plug.
b. Connect the black lead of the multimeter to the engine ground and the red lead to the CDI box's output terminal.
c. Turn the ignition key to the "On" position.
d. If the multimeter reads a voltage between 200V to 400V, the ignition coil is functioning correctly.
2. Using a spark plug tester:
a. Remove the spark plug wire from the spark plug.
b. Attach the spark plug tester to the spark plug wire.
c. Put the spark plug back in the engine and ground it against the engine block.
d. Crank the engine over.
e. If the spark plug tester sparks, the CDI box and the ignition coil are functioning correctly.
If the CDI box fails either of these tests, it will need to be replaced.
