Vibey 426...any ideas? I was riding a hot, loose, sandy trail on Saturday and my '01 YZ 426suddenly developed a bad vibration in the engine for no aparrent reason. I did not feel any significant loss of power, it starts fine and does not kill, it does not sound any different either--just this deep, intense vibration. I quit riding for fear of doing some damage. If it were a car w/a flywheel it felt like it was oblonged and something spinning very fast out of balance. it is in the engine,because it vibrated when idling. I looked for any previous postings on this topic and I only found a reference to a counterbalancer adjustment on some thread for a 650. Does this 426 have a counter balance? Would that randomly go 'out' of adjustment and cause this type of vibration? Does anyone have an idea of what may be causing this vibration?