cannot set mixture on '72 series 2

Hi, have come on here in desperation. I have changed the zenith carb to a nos replacement. I have the haynes manual. I follow the instructions which says screw the idle screw till it just touches the stop...adjust a further turn.....I screw the mixture screw all the way in then back off 1 and a half turns......start the engine....will not tick over....adjust the idle so it runs.....then adjust the mixture screw....no matter what way you turn the mixture screw it constantly runs over rich and you cannot get the engine revs to change...the exhaust smoke is blue and although it drives and revs it never sounds very smooth....What have I done wrong?????Please put me out of my misery Alan

yer main problem being its a Zenith nos carb,they have issues (warpage) which a quick search will reveal.