I've always felt that my 01 1500 carb classic had more vibration than my 02 FI Nomad did. This year it feels like the vibration is getting more intense. Do the motor mounts on these go bad in time? Could spark plug condition make it run rougher? It seems to run fine, I'm just noticing more vibration in the seat and bars than I remember. The bike has 19,000 miles.