RE: zdz 50ng broke alone
Hello! Looking the photo of the crankcase, it didnÂ´t seems like a fatigue brake, so i think is not a problem of vibrations. How were the conn rod, cylinder and piston? One possibility is that if the bolts from the oposite side of the broken area were untight or loosed (i.e. fatigue or over torqued), the tight side were supporting the pressure from the combustion chamber and causing the crankcase to support a momentum, not only traction force. Hope to be helpful.