Motorcycle Repair: 76 sportster pist-off, dirt bikes, plug holes

Question
Hello , I just got around to inspecting inside the spark plug holes on the 76 sportster that had died and lost compression, and IBD if there isnt a dime size hole in the top of the piston in the front barrel. So its a top end job at minimum ( I did a few single cylinder dirt bikes as a kid, hope this isnt too much more than that), but I guess my question is what are the usual causes of this?
The obvious possibilities in this case are running low on oil?, Can a bike being a little off time cause a burned hole in the piston? Does runnung lead in the fuel or not running lead in the fuel have this kind of impact on a piston. I was running led with every third tank full, but the guy I got the bike from said he did not run led additive just straight out of the pump. Any other possible reasons for this trauma.? Any advice on this rebuild. The bike will sit for a year or two now, while I start getting parts for it. Thank you.


Answer
A hole in the piston can be caused for overheating, pre-detanation or the valve hitting the piston
You would have to take the top end apart to see what caused the problem
if you are planning on doing the work yourself you need to get a service manual to follow so you know the specs
Not running lead in the gas will not cause this problem
Good luck and happy riding
Mike