Maxwell wrote:

Not a stupid question at all. In fact it has been done to the air-
cooled VW head and isn't all that hard. Far less work than making a
casting. IMHO water cooled aircraft engines have some real
advantages.

If this is that simple, perhaps it's worth doing. There is a small
electric water pump used in Mercedes-Benz heaters that could be used with
a motorcycle aluminum radiator that just might to the job... It's worth
thinking about anyway.

Many sport bike radiators can be had used cheap off eBay because they're
so well tucked in that they don't get smashed when the bikes crash. I
recently bought a Kawasaki 500 radiator for $12...

Tony

While this might be a good solution for some builders and designs, I would
test the radiator at 75% power for an hour or so before wrapping an aircraft
around it. Motorcycles seldom run at 75% power long enough to over heat. You
might need a good bit more radiator.

Actually I was thinking about using 2 of them but there are other bike
radiators that are larger. I'm more worried about welded in water
jackets cracking than not being about to get enough radiator surface area.

Tony