1996 720K PROBLEM......

I have a 1996 720k with 1074 hrs. and the problem is when I go from Half throttle to full there is a strong vibration happening right under the seat area. When it kicks in to full throttle it goes away. Same if I go from full to half throttle. I noticed that the left side pump fan is a little wobbly but not loose or anything. I got this mower from a family member for free and they bought it new in 1996 and always serviced it properly. It has sat up for over a year though. I have already changed oil and filter, cleaned carb, and have a little list of things to order for it . Like new steering dampers, fuel pump, pump fan, a couple of pto switches..lol..and some new belts. other than the loud hummmm with the vibration it runs pretty good. So if someone could chime in and help me figure this out I can add to my parts list and get this thing going...



Thanks, Chris