new to the posting thing and this site seems to guided many people proly better than a service manual, so why not join. so here it goes. already had 01 550 love it runs great and ive never touched it. so I needed another, bought a 02 550 fanny (3500mile)blown up. hole melted right in the middle of mag piston. story I got was, when dude bought it had no compression(old pistons look like ring stuck) so he put spi pistons in it and it last 12 miles. burned hole middle of piston, my thoughts it was sucking air? so I torn into it and its finally going back together. Cleaned aluminum off cylinder wall and rehoned looks amazing for just burning down .0005" clearance with wiesco going back in it. cleaned bearings. new crank seals. going to clean carbs. what else is recommended so It don't toast again, not knowing why it did the first time........