I have both a 6 and 9hp turf revitalizer. They both share one very annoying trait. They both have this real bad vibration that come from the front of the machine. It's noticible when sitting but when you turn on the cutters it will wake the dead. It seems like the sound comes from the removable belt cover to the seed agitator or both. Any other owners have the same problem and how did you fix it, or did you.