Ain't is a shame when a motor is so strong the case just can't contain it? But hey, over 2 years of desert racing and the crank looked like new. You are lucky the head just didn't fly off on its own.
Thats is exactly like the case that snapped on my St Anthonies Special. Except the crack opened up wide enough to see the crankshaft . I really think those cases with the grey coating have some issues. They have way to many sharp edges which are perfect for creating cracks.