Aesir,
You have a large variety of engines available for gyros, from the samller rotax to a IO-360.
A lot of amateurs also fit skidoo, moto or small auto engines that work fine.
You're very right to say, the main cause of accident is the piloting, not the aircraft or the engine.
I should add that an engine out is not a problem in a gyro, a great safety feature.
I am curious about how an helicopter engineer could adress a small gyro design..
Thanks
Victor