Why does my snowmobile make a bang when trying to start it?

[codak99]

I ussualy like to get te sled started every few months just to let the engine run so i know its in good condition for when snow flies.. Today when i went out to start it, On three seperate ocasions while pulling on it, It made a very loud bang that sounded like a gun shot. After the third i stoped thinking there may be something wrong and because i wanted my ears to stop ringing.. So anyone know why i would do that? I had the choke on full and was starting it like ussual and it was low on gas..