Wow! All this chatter & only one response that even attempts to provide useful info. (Thank you by the way.)
Actually, the engine it would be replacing is a Lycoming O-290G, which is a ground power unit engine converted for aircraft use. So, it wouldn't be replacing a true aircraft engine with a motorcycle engine. The dry weight of that engine is 264lbs, with fluids it is going to weigh in around 270+lbs. Concerns over CG issues have already been considered.
Concerns over watercooling are also misplaced. Watercooled aircraft engines have been used very successfully for longer than most of you have probably been alive. (See P-38 Lightning & P-51 Mustang for 2 examples.) The watercooled engines offer many advantages over aircooled aircraft engines. They are more efficient because they don't use fuel for engine cooling as aircooled engines do. They don't have problems with shock cooling as aircooled engines do. Multi-coil ignitions eliminate the need for dual magnetos. Also, bear in mind that the general aviation aircooled Lycoming & Continental engines are based on 40 - 60 year old technology. Still these engines will cost you around $26,000 for a 200 cubic inch, 100hp product, a 560 cubic inch, 300hp product will cost over $50,000. Whereas newer auto & motorcycle engines are based on state-of-the art technology which is generally more powerful & efficient, are just as reliable, if not more so, have greater parts availability, & are MUCH cheaper.
As for "homemade" aircraft crashes, the primary concern after the event is WHY the crash occurred so that similar occurances can be avoided in the future. Generic comments on aircraft accidents involving "homemade" or experimental aircraft without an examination of WHY the accident occurred are meaningless.
For anyone with a SERIOUS interest in this subject who is looking for similar info later on, additional research has shown that a better option appears to be the Suburu flat-4 or flat-6. the flat-4 comes in 3 variations: 170hp naturally aspirated; 225hp turbo (Forester model); & 305hp turbo (Impreza WRX STI model), all cost less than $3,000 for a used engine. With only moderate tweaking it will produce in the neighborhood of 460hp. All of this at a weight of only 260lbs including radiator & intercooler when stripped of non-essential items. Also, small bock Chevy engines are being used with great results in larger aircraft.
Last edited by merlain7; 09-19-2010 at 06:35 PM.