I have a 97' Ski-Doo Grand Touring 583. I went riding two days ago it ran perfect fouled one plug in the middle of the ride but it was when we were riding in powder. I went home let it sit til it idled. Yesterday I went to start it and it started up warmed up just fine and idled at the correct RPM. I went to take off and rode it just down the road during this time I was at almost full throttle it was running at the correct RPM for the throttle input but it was only doing 20MPH. It would sound every once in a while like it wanted to run normal but then dogged down again. I asked my friend and he said he had problem like this with his quad he said the crank seals may need to be replaced. Has anyone had this kind of problem or know what the problem is. I would really appreciate the replies.