A distant relative of mine wanted to buy a Honda XL500s. He found a deal on evilbay and went to look. He was told the engine had had a $1500 rebuild at a bike shop and had not been run in. He bought the bike and trailered it home. Next weekend was a club ride and he took his new purchase. He rode sedately for 20Km out of town and thought 'it must be run in by now' so gave it full throttle for the next 20Km to catch up to the group. He just caught up as it locked up, leaving a long skid mark on the road, and was able to pull the clutch and roll to a stop. After cooling down it turned over and started again but was sounding like a handful of marbles in a jam tin. He rode very slowly home with a blue haze following like a two stroke. It has been sitting for three years in his shed until he asked me to help. I've taken the barrel off and shook my head at his stupidity (which he agrees to) and this is what I found. Scored barrel with alloy from piston 'welded' to cylinder. Other side. Head gasket was starting to blow too. Have ordered new piston and gasket set and will be back to see the re-borer again.
I have my doubts about the $1500 bike shop rebuild too. The cam cover had been sealed with far too much black silicone which could have found its way to blocking an oil feed. And who would replace the domed head nuts with industrial flanged nuts? You can see how the self locking 'teeth' have chewed the copper sealing washers. Lots of other little stuff makes me think this wasn't done by a shop.
Not sure on the XL Thumpers but the early SOHC Air cooled run much tighter bore clearances than many bikes.. especially if compared to British Bikes.. and they do need to be run-in.. lots of people with more knowledge than me recommend only Mineral Oil while running in as well.. Geez... just saw the next lot of pics... if that was done by a bike shop... they should be named and shamed..