That sounds suspiciously like a grounding wire that's either come undone or has broken and is making intermittent contact.
If there was a belt poofkaboom, I'd look at the harness anywhere near that happening.
The electrical line that runs along the frame in front of the primary clutch would be what I'd look at first. Check the insulation and see if it looks like it's been violated in any manner.
Also check the ground leads off the CDI and the regulator and make sure they're still a) grounded and 2) not damaged or broken inside the insulation.
If the copper wire's toast inside the insulation, the wire will bend more easily at the point of badness.