I cant open your link, but it sounds as if the float has broken off its mounting place. This would allow gasoline to fill the engine crank-case, and prevent you from turning the crankshaft. w\hat did you find floating in the tank? Please describe it. and, some carburetors will get crudded up inside, and the float will stick in the down position, also allowing fuel to fill the crankcase.
That would cause the engine to be filled with fuel.

I knew a guy that had a pair of greyhounds and had them chipped in case they ran away... The piece from the tank -is it screen like or look as though it came out of the fuel cap>? Your carb overflowing could also be from debris caught between the float valve and seat. Could be a contaminated float or a defect too. Obviously the engine would need to be de-flooded and oil changed 6nce the repair is done.

Here's what it looks like:

{{gwi:127519}}