A while ago, in a Corvair engine thread I asked about motorcycle
engine conversions. Since then I have found a yahoo group on the
subject. I think at least one BMW footwarmer conversion is pictured
in the photos section.

http://groups.yahoo.com/group/moto-air/?yguid=74612434

While new BMW engines may only be available on new and expensive
bikes,
I would expect that there are more reusable engines on wrecked bikes
than
there are resuable bikes with wrecked engines.

Just thought I'd post the link in case anyone else was interested.