Ok I got a 96 xcr 600 with about 300 miles on rebuild. Took it out this past weekend and when I would let off the throttle it would hold at about 4000 rpm for a few seconds then idle back down to about 2000 rpm. Its never done this before, any ideas what could be causing this, I thought maybe it could be carb freezing up, rode in a lot of fresh powder, but I let it sit in the garage over night and all next day, and it still did when I pulled it out to put the wifes car in. Any help would be greatly appreciated