I was riding to work the other day and felt a clunk. Then I felt a clunky vibration by my feet. Sitting idle the motor runs fine, but when I ride it's like running over a rough road. fourth and fifth gear is better, higher rpm is better. 1st and 2nd is worst at low speed (rpm). However at higher speed a can hear a rattle, like a loose nut and bolt tinking against steel. Up hill is bad too.

97 Road King
Screaming Eagle Motor

 

Did you ever figure it out?

 

Shot in the dark here, but could it be loose/worn motor mounts?

 

compensator bad, maindrive gear bearing bad, wheel bearing bad. inner primary bearing bad, rear pully loose, front pully loose. i'm betting on something in the trans. lots of bearing problem on late model harleys