MSD issue

So I took the scamp out to warm up to flush radiator. Seemed to run ok. Pulled into the drive shut it off to cool to drain. No fire when i went to start. I checked for spark using the coil wire. I got spark when flipped to the on position but no spark in run. I have a street fire box and is connected the 2 wires together from the old ballast that connection is good. Where else could my issue be? Guess im not even sure where that power comes from. Fuse or breaker of some kind?