After double, triple and quadruple checking the entire fuel system and the entire ignition system. On the last running test I noted that the issue was a LITTLE better with partial choke enguagement.Has to be lacking fuel! Back to the carburator for the 5th time! Everything still looks perfect all passages clear and clean! I had previously done some surfing on this board and came back to it today and sifted through all relevent articles going back to at least 2007. I decided I obviously had a carb prob and had nothing to loose by drilling the main jet and the 2 lower orafices on the venturi nozzle tube as once suggested by RUSTYFARMALL on this board
a few years ago. There were several folks with varios idea's different size suggestions etc. I ended up drilling the main jet and both lower tube orfice's .062". The carb adjusted out and the tractor runs PURRRRFECTLY!! As I knew it should after the major inframe O/H. I guess the sorry gasoline we pay too much for today,milling the head and freshening up the cylinders raised the comp enough to require more fuel than the machine was designed for?
Again this is a 1950 M barn find original everything, paint decals loaaded with options,little to no rust anywhere etc!! I'm glad it's solved!

Thank You Rustyfarmall,Yooperfarmall,Laboyteaux,IHredo4,
Dukester,Ohiohillbilly,47farmallm,teddy52food.

This thing runs so good now I think I could latch it up to Iowa and drag it all the way down here to Texas!

That is great news.Now how about a picture of the beast?!

Good for you! Not sure I would be so quick to blame the gas. More than once, I have found hard clumps of corrosion inside the jets. Not sure what exactly it was, but it was ther none the less. you could see and blow through them, but they were restricted.

I have used torch tip cleaners to clear them out. Drilling as you have done is also an option.

Yeah, where are the pics?!?!??!?

Measured some main nozzles over the years. Best info I come up with is the nozzle for a gasoline M furnished in the fire crater piston sets. Top hole .069, middle .043, bottom .063, tip .136.
In original 50983DC carb. Top .042, middle .046
bottom .053, tip .111.
Some aftermarket in kits. top .040, middle .046, bottom .055, tip .111
Power improvment pakage for a M. Top .053, middle .062, bottom .070, tip 112.
Main seat or jet was bigger also in the firecrater set and smaller than stock in the power improvment package. Also the total spark advance was decreased with a firecrater complete kit parts.

There were no obstructions I inspected all bores and fuel passage ways with a borescope.

I will be posting pics this afternoon

Welcome to power tuning, the original engines were probably tuned a little lean, any compression increases and bore increases requires more fuel, you did the right thing by increasing the jet size. Just check the plugs to see if they are a nice color, (grey/brown) not black.