Why does my 03 ski-doo rev 800 not stay (with dry gas added) running when the outside temp drop below 20 deg?

[adam p]

Runs fine for a minute, then runs poorly. I have to put the choke on full and hold it at 3000 rpm for 2 to 3 minutes just to keep it from stalling out. After that it runs very well. But if it stalls during that time I have to put it in a heated area and warm the entire snowmobile up (takes a couple of hours) just to start it again.