Woah, look at this, what happened?

[Royboy]

Motor yes, with enough time and money and effort you could probably bring it back. If, as you say, the frame looks like that too I would be concerned about it's integrity. A wire wheel and a coat of paint won't fix weak, degraded tubes.

roy

 

[gggGary]

Cause? Well it probably wasn't due to excessive maintenance...........

My bet is a sticky valve hanging open, the piston hits it bending the stem, mayhem ensues.
This is not rare. Hint; when waking up a long dormant motor, pull the valve covers hit the valve stems and cylinders with PB blaster or other penetrating lube, kick the *itch over a bunch of times with the plugs out, set valves, cam chain etc. kick it some more before attempting a start.

Here's a shot of a similar event.

There were piston chunks out in the air cleaner.

Because I'm a slacker the engine became a light weight mock up shell.

Someone bet a guy he couldn't crush a 6 pack of empty beer cans with his forehead. He won. Oh, he died the next morning of a brain hemorrhage, Oops.
Carry on.

 

[badassjamie]

Ding Ding Ding! We have a winner. gggGary had stuck valve and the resulting damage.



Gonna bring her back tho!

 

[sseres]

isn't that crazy how banged up the piston is circumferential, considering the 2 valves are in a fixed position, and the piston doesn't turn.

 

[gggGary]

Once valve stems snap the valve heads move around freely. Both his engine and mine busted the bottom of the cylinder liner off when the valve head dropped through the hole in the piston and wedged between it and the crankshaft counter weight, (you can see it in his pic #5) finally stopping the mayhem. Revolving at 50 times a second I think the damage happens quickly.