Its commen sense not to shut an engine off right after working it hard. Sleds will often backfire if you ride them hard and then shut them off right away. Actually any carburated engine really will do that. Let it idle for a little bit before you shut it down. Its not good for it to backfire and its more likely to happen in warm weather. If you run 2 miles and then stop without walking it off or stretching your calves will tighten up stiff as a board. Engines dont like to run ragged and then suddenly stop either.
Be good to her and she'll be good to you.