You can take the CDI to the dealer and have them test it I believe. I may be wrong though? In order to test it, I have always done what STClarke has mentioned, swap in a different unit. Now, make sure you have good grounds at the coil. The coil is mounted to the frame, and it gets a ground through the mounting bolt, as well as the black wire. Be sure the pickup coil is gapped properly. .020" I believe is the magic number. check out BenBB's Banshee electrical FAQ on his site. CLICK HERE to check that out. Also, be sure that the key is on, and the kill switch is in the run position. Sounds stupid, but it has been done before....