Okay, Have to thank AV8TOR for helping me out with the carb problem. As I mentioned above the ZAMA, mylar diaphram does not like the nitro and AV8TOR tells me he has used the Walbro with a different diaphram material (which I have) with no problems so If you read my "carb search" thread you know what I am doing. I needed to match up the bore of the 11mm Walbro with the manifold I have and could not enlarge the hole in the manifold any further so, I have made a step down adapter from a 40cc Poulan chainsaw manifold. For me this was easier and faster than constructing an entire new manifold. I beveled the inside of the adapter where it fits inside the carb so there is a smooth transition. The ring will be JB Welded to the existing manifold and held in place when the carb is bolted up. Good seal between the two and no interference with the butterfly. Here are some pic's.