make sure your carb and exhaust is tight before you crack it open and see its something simple like that. also theres a decompression switch that sometimes sticks open. on the RIGHT side of the bike on the head theres a lever. make sure its all the way to the RIGHT. it should be almost touching the fins when its off. if thats the problem take the cable off and take some little wire and tie it so its down and stays down. thats what i did with mine. otherwise its proably rings or valve not seating right. what does your plug look like?
1999 Durango - In-Dash DVD, so far. More to come soon.