I have an 1989 skidoo safari with a rotax 503. I am having a wierd problem with it. When I am trail riding the engine keeps dying. It will run fine for a while and then just shut right down. still time i took it out it was running good and it dying i tried to pull the engine back over and it wouldn't move like it was seized up, then i waited like 30 seconds and it pulled over fine and started right up. then i went down the trail a little ways and it quit again, it kept doing this two or three times. It finally quit for the last time. i got off and pulled the spark plugs they were fine, i put then back in and then i primed it a few time and it still wouldn't start. took the plugs out again and they were bone dry. so i put back i and try to flood it with the primer by pumping it a crap load of times and then pulling it over. i pulled the plugs out again and they were still bone dry. so i left it overnight and went out and 3 pumps to the prime and it fired right up. the thing is it only acts like this riding it out on the trails, if you ride it around the house it will run all day with no problems. Anybody have any idea or info? Please Help!