Hi, at least the main source is found. (gasket)
Yes, cold revving and kind of things make sense.
Okay, bearings could have suffered, but this is easily to be seen when head and cylinder are off. It ran with its dry cylinder and probably steamed its coolant out.
In the industry we had rubber bearings, size of a soup plate, which were water-lubricated, worked for years without probs. I know, I compare....
