I have a 2001 blaster 200 that I bored 60 over. Its ran like it had a vacuum leak. But while riding it started shooting sparks out of the exhuast. So I replaced all the seals to get rid of the vacuum leak. Now when you try to crank it over the piston sometimes moves and sometimes doesnt move at all. It has some compression. Enough to run. I'm sure it's due for a new top end. But y will the piston only times move?