Roggy-

Jens' post reminds me I believe there were two quite different T4-80 designs. The one I was referring to has both the intake and exhaust connected to the head. I believe there was another (of which Jens' description reminds me) which drew intake through the carb into the crankcase - I forget how it got from the case to the combustion chamber. Then again, maybe I'm all wet.
-Dave