I hate to keep making extra posts, sorry, but this is interesting stuff. Also don't mean to keep comparing motorcycles to airplanes but they have many similarites at least in 2 stroke vs. 4 stroke. In the 1950s and early 1960s the same rules applied to 2 stroke engines that apply to 4 stroke engines today. The rules makers wanted to see more competetion from the 2 strokes so they allowed them to be twice the displacement. In those days the 2 stroke need more displacement to make equal power. So we've seen it go full circle. At least for the time being 4 stroke engines are receiving all the research and development. They are the engines that will get better. The 2 strokes are remaining the same until something changes I still see the 4 strokes getting better and better. Look at how many more 4 strokes are introduced to the marketplace than 2 strokes. The only new 2 stroke I've seen in a while is the Evo 100 and the 46AX. But YS has introduced a 63, 110, 140, and 160. Saito has a 82, 100 and 180. OS has introduced a low cost 70, a high cost 70 and I'm not too sure about Magnum, but I think they introduced a couple of new 4 strokers. Anyways, the market seems to be driven to 4 strokes.
Thanks,
Barry