Swlarcham:

Your coments about four stokes are wellcome too!!, the only thing that i start this thread about a 90size engine is that i think is much more simpler the use of a 2 stroke rather than a 4 stroke(and more if is a YS!! je je).
Like i said at the begining........i think that company like OS should develop a good .90size with pump intended for persons like me that we are flying 90 size pattern airplanes or 3D. Besides that, OS should also consider re-designing their four stokes to make them lighter like they made with the .70 size ULTIMATE.
Another option could be that YS could start making the YS91 for Helicopter for airplane too.