This is a pic of a PA50 motor for sale on ebay.
It broke the left end of its crankshaft off.
Thats what my original PA motor did several years ago.
The left end of the crank is pretty small and sticks out almost 4" .. maybe 5/8ths inch diameter.
.. and it has the pretty heavy starter clutch and variator on it.
I think if you rev them too high too often ... thats what happens.
(the motor still runs .... till you shut it off)