The other day the piston skirt shattered on my 2001 CR 250. I am wondering about causes. It has had about 3 Wiseco top end jobs in the past. This time we used Vortex because Wiseco was out of stock. The new Vortex had about 5 hours on it when she blew. I'm wondering how it is possible that there was too much clearance between the cylinder and piston??? Could the cylinder be worn out already? A piece of the piston went into the case and made it so it wouldn't turn over so I thought it was seized until I got it apart. I didn't force it or anything so the bottom end should be ok right?