Gerry
I had a similar piston blow some years ago, no big bang or seizure, just stopped as if I'd run out of petrol. Found I'd been running with too much oil, which can be worse than running with too little. That could be what's happened with you..??
good luck on the re-build. See you later in the year when it's warmer (fair weather rider me!
) and when I've put a new engine in mine.
All the best to everyone. Martin