I have a 250cc roketa that died one day and would not start. I found I had no spark. I tried a different coil from another bike still no spark. So ordered a replacement CDI. It run great for about 20 ft. and died again. Got it restarted but ran poorly and then died. Now no spark again. This bike has the 6-pin dc CDI. The coil used to test with has the A/C CDI. Would that coil blow the CDI? What would cause the CDI unit to fail?

 

When a CDI fails it can be just old age, but it can also be because some other part of the system is faulty and has overloaded the CDI. Always check the wires to the CDI are within spec before fitting, and check battery voltage (14.5V max when running), immediately afterwards as a faulty regulator can blow the CDI. The wrong coil wouldn't help and Chinese CDIs are of poor quality so you could have bought a dud.

 

Check all your connections including unwrapping all the solder joints in the harness. I the same issue on a import and found that one wire on the key switch was only hanging on by a thread. When i started going through the harness i found a few really questionable solder joints in it so i pulled the whole harness apart and redid every connection. Never had a issue since.

 

Ok. Got another CDI. Installed it ran very bad. Installed the original coil and all is well. I believe that the a/c coil is not compatible with the d/c system. Thank's to everyone for your help.