I did have success with removing spray paint from my car once. I had backed out of the garage and accidentally ran over a can of spray paint which then shot up on the side of my car. It wasn't a lot, but enough to annoy me. It was like over spray. I used acetone and I did manage to remove it without hurting the factory paint.

However I imagine that the factory car paint was pretty tough compared to the overspray from a leaking can of spray paint that shot up on the side of my car. I didn't remove the paint though for a month after it happened, it wasn't a lot.

If the bike has been completely painted and cured, it will probably be next to impossible to get off without harming the base coat.