carb rebuild problems

hello all, looking for some advice. I have just done a rebuild of the Zenith carburetor on my 2.25 series 3. I have refitted it but am having problems setting it up. Loads of black smoke from the exhaust and from the breather on the manifold, particularly at idle speeds - seems better at speed. The mixture screw seems to have no effect really and I cannot get the engine to run smoothly. I am sure the neighbours are p$ssed off with the smoke on the street

My next plan was to check the timing was OK.

Does anyone have any advice? Cheers Andy

andy i dunno about zeniths but it sounds like its running rich.
you may need to lean it out a bit. do a google for setting up zenith carbs and keep at it , you will get there in the end , took me yonks to set up my weber dmtl.