There are resistance (ohms) specs. for the generator coil(s), the trigger coil, and the main ignition coil. Check all of these first. These specs. will be in a good service manual (ex. clymer, or haynes). If all of these check out good, be sure that there are no shorts in the wireing harness. Check the coil grounds for good contact. It is possible that the CDI maybe bad, but there is no way to test it. It can be assumed that if all other components check out good, then the fault is the CDI modual.