We can also look at the 2stroke domination in outboard motors and snowmobiles. If you look at power to weight it is hard to compete with the 2 stroke. There has been a push for 4 stroke technology here though as they have the capacity to "run cleaner".

Really though, for all practical purposes, it might be best to limit our comparisons to the available motors that we can use on our planes? To me it is not just as simple as 2 or 4 stroke, but what 2 or 4 stroke do you like and why.

I like my 1.08 O.S. 2 stroke enough to put it on a new Funtana F90 even after I have a YS110 on my Yak.