Don't know if this helps but I had a similar problem when I rebuilt my carbs on a 400, it would take off like a bat out of hell and then quickly die in the arse. The problem was in reassembling the diaphragms, I put the spacer under the needle, I know, stupid right, so it would run fine on the slow circuit, but as soon as the slides started opening the needle would stay up and i'd be running super rich, causing it to die real fast. I know your bike was running fine before the the painting, it just sounds similar to the problems I was having so thought I'd put it out there