Problem With Suzuki GS500E Ignition?

I have a 1990 Suzuki GS500E. Last week I rode it about 500 miles. Today i went to start it and it started fine and then 15 seconds later it just died. I tried to start it again and nothing. Then i did all the testing to figure out what it is. I tested the coils and they were good, I tested the signal generator and all was good there the last thing was the ignitor/CDI. This cant be tested so i went to the local used parts store and got a used one. I hooked it up and it worked bike started right up. 15 seconds later it was gone again. I have tracked all the wires back and nothing is exposed and everything is hooked up right. What gets me is that just last week I rode it for at least 500 miles. any help would be great. Thanks