As a biker for over 30 years legally and more otherwise, there is no way I would put a Harley engine in an airplane. You want a dependable engine in there and NONE of the Harleys are that. Even the new one was brought out with a KNOWN oil lube problem to the valve train, and they introduced it anyway. I showed this to my brother after he bought his 2000 and said he better correct it with an aftermarket fix, he did not, and it went bad just like was explained in a biker magazine.
My newest bike is the Yamaha Midnite Venture, fully loaded and standard 5 year warranty with 24 hour roadside. Harley has shit for a warranty cause they got shit for a bike. Don't even bother to start talking American Iron till you research it. Quite an ad campaign they have built up in lies. Steve McGee KR2S