Jim Burk used to race one, and although I never got to look inside the crankcase, I did have some time to play with the cylinder head. I had some minor issues with trying to get the circle-square-circle of the manifold/intake port to flow, but I really have to say that the Tecumseh engineers really did know what they were doing. The valves are what Briggs engines dream of being. Might I also add that, lucky for you, Tecumseh ran a Walbro carb for a while, at least that's what I seem to remember. George can accurately answer that question.
