Well, just letting you guys know I did get my O.S. 91 put in my 4*. I did have to do a little modifying, but nothing major since I did have it set up with my 2 stroke first. I just finished doing the break-in by O.S. instructions and ran the two tanks thru it. WENT PERFECT! It is great when you put a brand new engine on and it fires off as soon as you hit the starter. I am sure many other engine brands are just as good, but I have to say I love the O.S.
At the end of my second tank for break-in I set the needle valve to what I think I am going to like and when I would idle it all the way down it just sat their and would idle all day I think, but when I would shove it to full throttle it would rev up and not think anything about it. It also sounds like it would pull my truck off the ground. All I can say is that I am very happy with it and I know I will be buying more four strokes.