My brother has one (that's fixing to be mine ) on an ultimate bipe (.91 2st) and it's a screamer. Very strong engine. He runs (I believe) a 14 X 8 prop on it, and it will pull the bipe around like it's nobody's business. Never had an issue with it--great running engine. Another guy at our field has a .75 asp and it's a great running engine as well. My understanding is that they are (were) made by magnum. Don't know if that's true or not, just what I've read.