Talked the a shop owner today who just got back from a 2003 pow wow with the big dogs from ski-doo
he said to expect a tech update for carbs to stop backfires on shutdown for the 700's they are aware of the problem and are working it. Mine only did it once so far after along run, now I let it idle for 10-15 secounds and shut it down hasen't done it again.

My 700 also give me a little * !poof! *when i kill it somtimes.

Keep the heated carbs turned off. Virtually eliminated backfire.