Barn find shake out check out after 10 years idle.

Finely got the 1996 bear cat 550 with 1900 miles out on the snow I bought it last spring and this was the first time on the snow. Prior to taking it out I went thru a checked and replaced the pugs, oil, Gas, greased everything. ran it on the stand everything worked as expected .Then I took it to the lake and it started on the third pull with choke on after warming up choke off it ran little rough at idle and will quit after 4 minuets of idle I'm thinking its just a carb adjustment or rebuild. I was pulling two ice fishing sled with one person each in the sleds on the flat lake snow but when i gave it throttle it would jump after hitting 4 to 10 miles per hour the jump was intermittent not consistent so i know it not in the hard drive train chain or gears. I'm thinking it is the belt that has been sitting on the machine while it sat in heated garage for nearly 10 years not moving. Any ideas or past experiences? Also i noticed it did not steer well on the packed snow like the skies were not making good contact they seamed a little higher off the ground than any of my other snowmobiles.
Note everything on this machine is still stock except the clutch that was changed to give it more lower end power.. also the starter motor was removed.