My background is automotive technician. I am a retired Marine and line tech. A friend has a 1945 G Allis and Chalmers tractor with a TSV 13 carburetor on it. He had the engine overhauled a year ago, and it ran great for about an hour. He said it started acting as if it was running out of gas, and has not run correctly since. 

I removed the carburetor, took it completely apart and cleaned it. I ordered a kit from Amazon to rebuild the carb, and replaced everything in the kit. While tearing down the carb, I noticed a foam type screen on the adjusting screw on the bottom of the carb. The kit didn't have this in it, and I can't find a picture anywhere showing it. I put the carb back together, leaving out the torn screen, and we still have the same problem. I adjusted the air/fuel mixture screw on top to one and half turns out. The bottom adjuster, I set at one turn out. The plugs keep fouling with fuel. I am not sure of the firing order, but the two middle plugs are always covered in fuel and the two outside are not. The tractor tries to run but will not. Puffs of dark gray smoke come from the exhaust when trying to start it. 

Can someone tell me what the foam type screen is for? The bottom adjuster seems very loose, and it seeps fuel from it. Could this be a timing issue also? 

Any help is highly appreciated.