I heard that the McCulloch engine usually used in the Bensen was actually an engine designed for target drones, only meant to be used once!
They were a constant headache, but had good power to weight ratio.
I suggest that you steer well clear of those old engine designs, however Autogyro“s with Rotax, Arrow or Subaru engines usually work out ok.
Its not the engine or the Gyrocopter that will be the cause of the crash, it will be a untrained or reckless pilot!