Could be the variable speed drive belt. I had this on the 570R I used to have. Certain RPM ranges it was fine, others not. Belt looked fine, didn't seem to have excessive slap. Swapped it with a used belt I had and my cylinder vibe vent away. On that machine the cylinder and rotor variable speed belts were the same if I remember correctly, one could swap them before throwing a $500 belt at it.