2.4 hours on a rebuilt 82 XL 500 and the piston froze (150' skid mark on dirt road, didn't go down:). I rebuilt it myself Bored cylinder 1mm over and went to a 12.5:1 Wiseco piston/rings. New gaskets, valves, v. springs, seals, and exhaust seats, professionally ground and lapped. Retained the 128mm jet (Honda went to a 135 later in '82). Haven't pulled engine yet. Presuming plenty of oil and a good oil pump, where'd I go wrong? Should I have gone to a bigger jet? Wiseco politely told me to ask my dealer what I should use after their piston install. Dealer, of course, said ask the piston maker. Using 91 octane w 106 octane enhancer and a gas stabilizer. Bike would smoke when cold and stop when warm. I figured it was the valves settling or the difference in expansion between the alloy piston and the steel sleeve. Air temp was about 95 and the seize happened on an extended mild uphill run in 4th at about 50. Informed opinions invited. Tks.