Work is slowing on my 30% Piper Cherokee built so today decided to look at mounting the Zama carb on the Roto 85 FS. This engine was purchased around late 2018. During the built the carburetor flange was broken on the intake manifold. Little info was available at that time and I purchased the engine from an importer on Ebay. Made up a piece of aluminum that is screwed and glued on with JB weld. The repair worked well over the 5 year period that I flew the plane. The second engine I purchased a few years ago has a much more robust intake manifold.
The hole in the intake is 1/2" in diameter, the original Walbro WT962 has a 14mm bore, and the new Zama needs a 20 MM bore to accommodate the black plastic piece. The plastic piece sticks out about 1/2" from the flange on the carb, see second photo. I plan the make a isolator plate out of 3/8" G10. The plastic piece is there for the idle circuit.