Well, Aesir said it correctly. The McCulloch engine was powerful (90 hp, I think) but was indeed prone to failure. My friend had a number of failures, once landing in a parking lot next to a highrise. He was so nervous about flying with that engine that he never left the local airport which included a large grass infield. (The airport is located on an island with the lake on one side, Toronto on the other.)
However, in fairness to Bensen, I never heard him criticise the airframe itself. I understand Bensens are good machines and his seemed to be pretty solid.
Speaking of engines, my friend spoke very highly of a Volkswagen engine, which produced about 60 hp.. I've lost contact with him and I don't know if he ever replaced the McCulloch with one.