Model B Carb issue

Hey guys I am back and still have not figured out the problem on my B.  I will start off by saying it is a zenith carb with only the idle mixture adjustment.  I bought a new sediment bowl and valve to make sure there wasn't something in the valve that was letting debris through the line to clog the carb.  I start the tractor and runs like garbage.  It is getting WAY too much fuel and I cant figure out how to stop it.  I've adjusted the float all over the place.  Originally I started at the recommended 1 5/32 float level from the manual, and I have gone all the way down to 1 9/32 and it is still running so rich that it is blowing black smoke and fowling plugs.  3rd set of brand new plugs and this time I bought autolite 295s like I was told to.  Besides rebuilding the carb, I have had it apart more times than I can count to clean it.  And I have cleaned every possible orifice that I can find.  Also, the idle mixture screw continues to be worthless in changing anything at idle, no matter what I do.  I can turn it in the whole way or take it the whole way out and it does absolutely nothing.  And I have tried adjusting it with the linkage rod held against the stop so the governor doesn't get in the way.  I cannot get the well vent out of the bottom part of the carb, but I made sure that it is free and have cleaned it out so that I can spray carb cleaner down it and see it come out in the bowl.  I so disgusted with it and I just cannot figure it out, despite all the recommendations and help I've received so far (I greatly appreciate all the help by the way).  I have good compression on every cylinder, good spark,  and getting fuel to every cylinder (way too much). Also, after I start it and turn it off, I can only start it again if I drain the fuel out of the carb bowl.  And even then it starts really hard.  Hopefully somebody has something in mind that will fix it, as I am about at my whits end with this thing.  Thanks

is it possible that your carb has the wrong main jet installed in it?

Edited by Dick L - 02 Oct 2016 at 7:46am

The idle screw doesn't do anything if the engine isn't running at a slow enough idle( low vacuum pressure). Dick might tell you what RPM to look for here? I'm sure it's probably slower than most people have an engine running when they can't "get the idle adjusted".

I didn't know it was even possible to put the venturi in upside down on that carb. I will check it out. Thank you