Compensater sometimes makes a loud knocking noise when shutting off the bike thinking of going with a later year, any year to avoid ? I think a friend has one off a 2015 I can get .
Might be loose check the bolt to see if it's bottoming out
Most likely very worn. You can put the 2015 in but make sure you add the drip tray to primary cover.
Start by reading this. If you decide to change the comp consider having the shim(s) on hand or at least measure it and order if required before you install. A loose new comp will do the same thing as you are experiencing now.
http://harleytechtalk.com/htt/index.php?topic=82010.msg917659#msg917659