I've had the '08 for about a month now and have about 2k on it. So I'm not totally familiar with this engine. What I feel it like a rhythmic knock running down the road. I feel it in the handlebars mostly. Thought maybe a bearing going bad? Sort of goes with the rotation of the wheel. If I pull in the clutch, I feel nothing. Notice it a little bit more under acceleration too. Even at idle sitting at a light I feel it slightly, so that kinda rules out the wheels or maybe even the drive train. Do these engines have a counter balancer that might give the engine and little dull knock as you ride? Do you all catch what I'm saying? I'm gonna try to ride an '03 tomorrow if it doesn't rain and see if his bike has the same feel. I bought the bike in great condition with 53k on it.