Model B Mixture screw problem

Hello All.  I am new to this site as I am new Allis Chalmers owner.  I have taken a look at some of the forums while working on my tractor and I have found a lot of information and really enjoy reading all the knowledgeable and professional feedback given on the forums.  Therefore, I have a question that I am hoping somebody can help me with...

I recently bought an AC B and I have gone over pretty much everything to get it running.  Checked timing, compression, spark, fuel, new plugs, rebuilt carb, new battery for starter(has magneto), and generally cleaned the fuel system the best I could.  Today after finally getting all that completed, I got the tractor running.  It was running decent at idle, but not perfect, and when I got on it and drove it, it begins to sputter and cut out until it finally shuts off.  I have played with the idle speed adjustment and the mixture needle.  I noticed tonight that when I adjust the idle mixture screw while it is idling, it does not change it at all.  I took the carb apart a couple times to see if something is plugged up (including taking the jets out and cleaning them) and cant find anything that is blocked up. The only thing I didn't remove(because I cant get it out) is the well vent,  but I did shoot carb cleaner in it and it shoots out just fine, so I don't think anything is clogged in there.  Why would the mixture screw not be making any change in the way it is idling?  I started with it 1.5 turns off seat, and both screwed it the whole way against seat and backed it all the way out, with no change either way.  It just idles the same way the whole time.  Hopefully somebody on here with more experience than me can help.

Secondly, where do I fill the oil bath air filter cup up to.  I can't seem to find any definitive guideline on where to fill it to.  I filled it so the whole cup is filled up to the holes in the center tube in the cup.  Maybe this has a little bit to do with my other problem?  Thanks to anyone who can help. 

goatflamm wrote: My carb also only has one adjustment (besides the idle speed screw on the back of the throttle lever).

That hole is a drain hole for over flow. It should have a small screen on the under side.

Then you only have to adjust slow idle. Again if the passages in the idle circuit are clear and you do not see a difference your stop screw is set faster than a slow idle. You are drawing enough air thru the engine that you are only using the power jet. In your case a non adjustable power jet.  A non adjustable power jet means that you have no mechanical way of adjusting it above idle. The jet can be changed or if you know what you are after can be drilled out as an adjustment.  

This should help some if you do not have a drawing.

Without looking I think it is about in the center of the hole in the center cup. I have one that is not marked as well. Most the fill line is a ridge that sticks out around the outside. Full will draw oil into the carburetor.