I have the same feeling. But it think mine is the shifter vibrating. i can hear it more then feel it. and it seems to be attached to RPM rather then speed. It is diffently on the front of the bike and low. Don't know if this helps but you might look. Mine started after a new front tire.....so i also suspect that maybe the tire is slighly out of balance. But if i figure it out i will post it.. btw this is an 01 heritage.