The Suzuki G13BB engine is about 15 lbs. heavier than the Rotax ready to fly. Puts out around 10-15 more hp and is very bulletproof, having been raced at extreme outputs in turbocharged form and many have been used in aircraft. Tampabayaerosport and Raven make gear and belt redrives respectively and most of the bugs have been worked out a long time ago. They would be a fraction of the cost of a 912 both to acquire and rebuild.
Lots of info at: http://groups.yahoo.com/group/FlyGeo_uncensored
Lots of info at: http://groups.yahoo.com/group/FlyGeo_uncensored