There are about five different size pulleys to drive that wobble box from that start of them style drives in the 300 to today in the 7000 and 8000s. If vibration goes away while idleing machine back some from rated load (2300 on R60)you may get by with next smaller pulley. If vibration gets worse you may want to get the largest pulley if that isn't what it allready has. I think ROMs flywheel idea would be best but I haven't went that far yet. Rigid heads these days have a flywheel on rear shaft but I think they would smoothen out even more with flywheel right on the wobble box. Good luck