I'm helping a friend out with an engine rebuild and I figured I would share here- bike "locked up" on him when out in the So Cal desert riding. I had no idea what I might find, but I think this might be the culprit.
It appears as though whomever did the last top end neglected to install one wrist pin circlip. 20 hours on this engine since rebuild. wrist pin walked out the left side, made contact with the cylinder wall, and then got cracking on destroying more stuff.
Thankfully the exhaust side of the cylinder skirt was there to take the hit from the wildly flailing rod, instead of knocking an inspection window in the front of the case.
Maybe some JB weld and a buffing wheel will fix this.
This is the future of four stroke technology. variable axis connecting rod. or not.
So kids- double check your work and make sure the retaining clips are in the groove correctly. Owner is now on the hook for another $800+ in parts just to get it back to normal.