I have a 1965 S65 I recently restored but can't seem to get the fuel mixture to behave - it's running extremely rich at idle. I've cleaned out the Keihin carb three times now, by soda blasting, dipping and blowing with compressed air. Replaced all internals with the exception of floats (which I tested and can confirm do float ok) Their height is set to 19.5mm as per the manual. Also tested them/needle valve & seat etc with the bowl off and they stop and start the flow of fuel as would be expected. Clue: Turning the mixture screw in either direction does nothing. I know most often this points to a clogged idle circuit/jet but I can confirm it's all clear. Valve clearances & timing are set to spec with a brand new air filter. Spark is bright and blue. Unless I'm missing something, could there potentially be an issue with the actual carb body? Possibly an internal crack etc that could be hemorrhaging fuel? It starts without choke and idles erratically but doesn't die out unless I choke it. Weirdly, it seems to rev out fine and smooth, but throws a lot of smoke and then dies when it returns to idle. Plug is dripping wet with fuel after a few seconds at idle. Follow up question: Anyone happen to know if an S90 carb would fit? The Keihin's for those models look almost identical but not sure about diameters/jetting etc. From what I've seen, they seem to be more plentiful & generally in better condition than ones for the S65. There's not a ton of support for these models but figured I'd try my luck here here since the engine layout/specs seem to be closest to the old CT70's. Any ideas are very much appreciated.