How to make this test work: tie spark plug threads to black wire,
Find a 9 or 12 volt AC TO AC adapter (not AC to dc) and a attach blue wire to one side of the plug (yes plug end) and the black wire to the other.
Now use your 9 volt to pulse the output wires of the transformer. If it doesn't work at first reverse the battery.
Reasons
Magneto actually generates between 10 and 100 volts At blue wire, 6 at white wire (9/12 volt transformer raises voltage)
cdi needs negative pulse to fire. ( transformer creates positive and negative spike( I think))
video:
http://youtu.be/USfugC8PAzU Note that I used a 12 volt ac to dc adapter in place of a 9 volt battery as my 9 volt was dead.
if you want to have a better tester and some fun at the same time use a second 9/12 volt ac adapter to derive the first one form an outlet, as shown in 2nd video.
2nd video:
http://youtu.be/hXKu8XqCQDE
I ran this setup for an hour and had no problems, the cdi was fine, the adapters were slightly warm.
Note driving the cdi directly from a 120 volt outlet might work, but is much more dangerous as the 2 transformers limit the current to about 25 mA, compared to 15 A. (actual current depends on adapters.)
This test has proven many cdis good and a few bad in the past year or so. The voltage at the blue wire es equivalent to running your motor at full speed, so it can miss a dieing cdi sometimes.
What will you take in trade?