My 09 SERG made this funky rattle between 2800 and 3500rpm... from day one.
All the dealership techs heard it, and yes, HD said it was "normal" I said OK, I'm gonna run it till it goes BOOM...
While I didnt ride it till it blew up, the lifters were the cause of this failure, (the roller needles failed, causing the roller wheels to stop and wear flat spots on both them and the cams, with the metal carnage working its way into the oil system)
My contention is that it was bad lifters hammering away at the cams all this time, until I finally encountered my flock of angry birds trying to get out of the cam chest. Pisses me off that I just changed the oil the night before everything went south...
Maybe I should have rode it for a few more days to make sure everything was all jacked up... then I'd have a new motor....
I hope to get her back before new years (christmas is very doubtful) and enjoy a night ride.