So I have a '97 Zl 440 that blew a piston two years ago, we fixed it and have been riding it a little, maybe 300 miles since then. So the most recent thing started at about the beginning of this year. It would start okay at the beginning of the day, but if you ride it, then let it sit for an hour or two, it absolutaly won't start. I was on snowmobileforum.com and the guys on there said it had to be a crank seal, but I didn't think I could replace that, so I just let it be and rode it for about a month. Now I think I blew the same piston I blew two years ago and am assuming that it is the crank seal that started my problems two years ago. Could it just be the crank seal that is making it not fire on that cylinder, or is it for sure blown. It has compression of 120 on the pto, and 60 on the mag. So now I just ordered two new crank seals from my A-C dealer and they will be here wednesday. I have never been inside the crank case and would really like some step by step instructions to do this. I am willing to learn, I just need someone to help me. Your help is soooooo much appreciated, so please help me.