Sorry my first post is selling something, I do plenty of reading in the tech area and haven't had anything to contribute yet ...
I have a brand new OEM ' carburetor for a 76 z50a and polished intake. I bought it to install on a motor I rebuilt, but I sold the bike and motor @ a discount and kept the pricey carburetor.
I haven't ran a drop of gas in it or installed a hose on it. I just bolted it onto intake a few weeks ago, kept it covered and clean. I have the throttle slide and top set that came with it.
I bought the carb from dratv.com where I paid about $132 shipped. I'll sell carb and stock intake for $130 shipped. Carb alone for $110 shipped. You can find cheaper carbs -- but they don't mate with stock intake. I made that costly mistake already :). Get the piece of mind that comes with knowing the carb is Honda quality and jetted correctly, and you won't have to alter throttle cable, etc.
*CARB_Z50'S K3_THRU_1981 CAN_WORK_ON (K0_TO_K2_READ) 32MM_PATTERN 7/10A (73S)
I am 100% on ebay with 138 positive feedback, by the way (username: mippitys).
Might consider trades for CT70 K0 parts. Thanks!