IH 300u gasoline carb questions

I just rebuilt the carburetor on our recently purchased 300U, but can"t seem to adjust it properly. when we got this tractor last year, it was having major carb problems(backfiring, stalling, not idling properly) and it was missing the idle speed adjustment screw. i followed the procedure for carb adjustment in the shop manual, which says with engine warm, turn the fuel mixture screw until an idle speed of 425 is reached, then adjust the idle speed screw until idle is smooth. even with the hand-throttle lever in lowest position, i can only get the rpms down to about 550 without the tractor dying. it also is running extremely rough at this point(way too rich), and turning the idle speed adjustment screw has no effect on the idle smoothness(it doesn"t appear to have an effect at any rpms). the tractor runs decently if i adjust the mixture screw until it is idling between 850-900 rpms, and is usable, but is still running way too rich, and sucking down fuel like mad. when i shut off the engine, fuel (sometimes) will start dripping out the carburetor air intake. anyone got any troubleshooting tips, or could this be a governor problem? thanks for the help.

#1 when ever you mess with a carb on that type set up you also have to readjust the gov. or most of the time you will have problems. Also that low RPM number is just a magic number that ya it is nice to get to but that is also for a new engine with every thing as perfect as it can be and with an older engine it may just be a dream to get to that point because it has been worked hard and put away wet a few times and will not go that low any more

I wouldn't worry too much about the 425 RPM, that is when everything is perfect. If the idle mixture screw has no effect, then your carb is still dirty. Disassemble, soak in real carb cleaner all night, and blow out with compressed air. Make sure all the jets are clean. I have never had to adjust the governor after rebuilding a carb. I'm not saying yours does not need adjusting, though. Set the main screw at about 3.5 turns out. Setting of the main jet on your carb is determined by load -- 5 turns out for a full load, less for lighter loads. Too far in and it won't pull anything. I assume you put a good kit in it and not one from TSC or some other farm store that sells cheap kits.