Stealth, the more you explain your problem the more it sounds just like my problem, although my tank vibrates with the bars and pegs. I put my stock seat back on and now my ass buzzes also :???:
I know it's engine speed related as I have tried everything else except replacing the chain.
Have you checked out this link:?
http://www.bikersoracle.com/blackbird/foru...read.php?t=6542
-Dave