I just bought a 05 kfx400, when I went to look at it the only thing that was supposed to be wrong with it was that the starter was bad. I get there and put it in gear and it rolls like it has 0 to very little compression. It wouldn’t push any air out of the exhaust. So I talked them down and got it pretty cheap. I get it home and start tearing it down and noticed that when you put it in gear and push it, the flywheel or anything else doesn’t move. So I put a ratchet on the flywheel and spun it over and it feels like it has decent compression and it’s pushing air out of the exhaust. After that I pulled the spark plug out and pushed it a little more and it seems to spin the flywheel a little bit. What would cause this?