ya i know but I pretty sure I didnt but you never know ? when i pulled it apart though the piston was in correct n I did s\check end gap though it was .014. when i dial bored the cylinder it shoed 64.994 and iston was 64.993. I questioned the tight tolernces. If memory serves me I think they have no bridge on the exhaust port and I remeber look at the ring flex into exhaust port and smooth back into landing when I did a mock up. the end gap was correct as far as stock tolerences go and was bore clearance. I strongly question the exhaust port but I havent heard anyone else having problem so I guess it must of been my fault or just a freak quality issue I remember once a pro-x pistong had a pistin pin retaining pin come loose and scar cylinder. except then pro-x la sleeve made good and fixed me up. athena wont even reply to any of my requests for a explanatin or something any communication but nadda . I will never buy anything athena again thats how I am. I remember when I was a kid I ran amsoil and my fresh bike blew and rod bearing. since them I will not run amsoil. LOL