that is weird. are the carbs synced and tuned right? also are the right and left exhaust pipes reaching the same temp. It could also be carbon build up in the pipe, or... a million other things.. If I were really concerned, I would run a compression test, and cylinder leak down test to confirm its not an issue with the head, I would then run a cooling system pressure test to make sure your cooling system isn't to blame, after those two check out good, turn to the fuel system and make sure the carbs are balanced.
Try parking on the centerstand over night. and see if it still smokes or if both sides smoke. Also try parking it in the opposite direction of how you normally park, maybe the left side of your garage is slightly cooler than the right.