Heck, that piston looks new to me! While you have it torn down go ahead and cut some scavenge ports in the intake windows of that sleeve....justr dont mess with the exhaust. Then buy a tower tuned pipe for 15$ and you wont believe how much power you will pick up. How about 15K rpm's with an 11X5. Then you can spank the other OS guys that are whining about YOUR engine that you decided to take apart. Problem solved.