On first blush, sounds like a fuel problem that you need to track down..
What is the history of the tractor, and the fuel that is in it? The more detail the better..
With fuel line off the carb, will fuel pump through the line?
I happen to be working on my L 130 with similar issues right now. Mine has the Keihin BCH 24 053 61 and will idle smoothly if fully choked. Cleaned it up this evening and will reinstall it tomorrow. Might be able to shed a little light on this in the next day or two.
You will want to know that the solenoid at the bottom of the carburetor actuates when the key is on. Set the park brake , turn the key to on and listen for the click.