On Sun, 23 Aug 2009 07:28:33 +0700, Bruce In Bangkok
wrote:

Given that literally millions of air cooled lawn mowers have operated
successfully with little (probably no) maintenance all over the world
it is doubtful that air cooling is going to be a problem.

As long as the engine is operating in open air, not enclosed in a box.
It would take a lot of forced air ventilation to get successful
cooling within an enclosure. Unfortunately I think most people would
want it in an enclosure for safety and noise reduction.