My 96' Low rider has developed an issue with the rear brake master cylinder. When I apply the brake the master cylinder smacks against the exhaust bracket. The bracket is an add on for the 2 into 1 exhaust. However that exhaust has been in place for years and the problem is only weeks old. Two shops have looked at the bike with no results. Next up is a Harley dealer here in Seoul. But the service tech's initial answer was to cut a hole in the bracket to give the master cylinder room to move. That might fix the immediate problem, but seems it ignore what is allowing the cylinder to move in the first place. Could this be a more serious problem? Any thoughts here would be appreciated.
Thanks

 

The rear master cylinder bolts directly to the frame. If it's moving either something is broken or the nut came loose. Either should be obvious with a cursory inspection from a half competent mechanic.