All of us who work on motorcycles, we have all been there; the painter or powder-coater forget to mask a thread. Taps and dies are good on small threads but what about larger ones? What if you're already fitted key parts and access is limited? Fill the back of any holes or spaces with clean rag and add masking tape if necessary.
Apply paint stripper (even the modern weak stuff) cautiously with an artist's brush then walk away for 30 minutes. Carefully dig into the threads with a pick, old tooth brush or similar to loosen the finish and vacuum off everything that loosens. Reapply the paint stripped and repeat the process until the thread is clear. Eventually the thread will come clean.