Never snapped a crank on a bike, my old T100 triumph threw BOTH rods through the front of the crankcase-that made a bit of a mess............... I have snapped a crank on an old VW Beetle once-driving across the paddock at Snetterton after a bank holiday race meeting-1970 ish, Vincent outfit on the trailer, 3 up and with about 2cwt of tools in the front. It started to vibrate and the oil light came on, I stopped and had a look and the fan pulley on the crank was moving in and out-I thought 'oh bollox-it's blown the crank shims' car was worth about 1/10 of the bike so we decided to carry on. Bank holiday traffic on the old A11 was legendary back then, the oil light didn't go out until we were doing at least 40mph-but we made it home to Essex. Borrowed mum's car to get to work the next day, when I got home I dropped the engine-before I did that I decided to see if it would start-first flick of the key! You could hold the clutch flywheel still and had + or - 16degrees of movement at the other end so the 2 cylinders driving the gearbox had that varience on their ignition and cam timing. The crank had sheared in half in the centre bearing-at an angle luckily-so there was some tenuous connection between the two halves. Been a fan of the old aircooled VW's ever since.
Snapped two cranks on my old 851. The first was the original large spline crank, and Ducati supplied a new small spline crank free. A year later that one snapped as well, and I got a corsa crank from Baines. That was a mere £500 in 1993.