Same problem with my 06 Speedmaster. I tried everything, it would not thread into the tank. I put some pressure on the cap, it would not thread. Talked with Brent and he said I was the second person in two days that had the same problem. Brent was wondering if the tank on the 06 had changed somehow since he had sold so many of these Kuriakyn caps to speedie owners without any problems.
Sent mine back for credit today.