Engine seized up as result of exhaust side of piston's skirt breaking apart and falling into lower end of engine. Yes there was engine oil and also coolant, both before and after the "seizure"... or that would have been a big lecture to the boy!

I read on another blog this is usually the result of running to lean, thus too hot and pop??? In hindsight, the bike was accumulating some oil/sand at the exhaust port/muffler connection on the cylinder. It was initiated by an over full oil condition, which was corrected, weeks before. But, maybe that popped the seal. The bike started, ran well, plenty of power, it was odd. Another blogger suggested it is caused by too much tolerance in the crank bearings, causing piston slap?

I have torn down the engine to lower end engine case splitting stage.

Cylinder has small gauge (about 3mm length, maybe 1mm depth and 1-2mm width) from top of port upward. Thus, top 50 - 60mm (about 2") of cylinder are perfect... which is combustion chamber.

Metal piston shards remain in lower end of engine. Although when I pulled the flywheel, crank broke free and permits about 200 - 270 degrees of rotation. And, rotation exposed many shards of piston skirt metal wedged in between crank, removed accessible metal shards, yet crank will still not complete full revolution.

So...
Questions are;

1. does the cylinder need rechroming or can I simply hone it to remove any high edges as the nick is so low in combustion chamber?

2. looking for guidance on how much to change out... lower end bearings and seals (about $60) or crank too (about $75)? top end kit (about $125) (depending on brand)
3. any experience/recommendation on engine rebuild kits; wiseco, nomura, hotrod cranks, moose racing - all offer a complete lower and top end rebuild kits from $260 to $400...?

4. any recommendation on cylinder rechroming companies? (us chrome)??

About 10 manhours to get top end, clutch cover, clutch housing, flywheel, flywheel cover and stator plate off, and remove engine lower end from bike frame... including all the requisite steps to begin those tasks. Likely a shop would do it faster. Only mention the manhours to give an idea to other weekenders considering the task.

Thanks in advance.

Repeating the topic doesent help.