Be sure to report back after you turn the piston around. Let us know if it fixes your problem or not. The shop manual is so lousy that it doesn't even mention the arrow on the top of the piston. My machinist told me to be sure to point the arrow on the piston towards the exhaust port. I wouldn't have even thought it made a difference. He told me if I put the piston in backwards that it would snap the rings off on the first revolution of the crankshaft. Apparently it took a little bit longer than that for you, but it sounds like he was right.