cavalamb himself wrote:

There was a Neiuport 12 project (two seater) published in Kit Planes a
few years ago. He used a Yamaha engine and transmission - locked in
second gear. (IIRC!)

Real nice article about the airplane and engine.

But no a mumblin' word about how the gearbox cratered a few hours into
the test period.

But, for Pete Sakes! Run a bike at 80% power continuously - in second
gear(!) - what do you expect is going to happen?

TANFL...

I remember seeing that article. Considering the engine they used and
how they mounted it, I'm surprised the engine didn't seize up first.
They used a Yamaha Virago V-twin mounted backwards so the shaft drive
would be pointed forward. I can think of several reasons why this setup
would fail...

A few year ago when I first thought of merging 2 of my passions (bikes
and flying) I was working on ways of turning a Virago engine sideways
like a Moto Guzzi engine. The only workable solution would have been a
custom machined side case to take power directly off the clutch basket.
This would give leave you with the built in gear reduction of the
primary drive but leave out the transmission. There are lot of things
to be concerned about in a conversion like this but the 2 biggest things
I think are; would the case hold up to the side loads and would the
vibrations of the prop over load the dampening in the clutch basket? I
think turning the engine sideways in the air stream would improve
cooling so at least that would be a plus in it's favor.

If I had enough money to work the problems out of this type of
conversion I could afford a new Rotax 4.

Tony