574 running rough

Good moring! I have a 574 gas that is running rough-sounded like it was missing or not all cylinders were functioning well-and I can not figure out what is going on. Here is what I know and did.

I checked the spark plugs and notice they all were covered in a thin, dry carbon film so I cleaned them, and regapped them. Checked all fluids-oil was good, radiator was low, so I added to full. I ran them for an hour or so and the tractor ran well but the "chugging" returned.

The spark plugs were covered in the dry, carbon film so I put in new spark plugs-Autolite 3116, points-gapped them to spec 0.02, condenser, rotor, and distrubutor cap. One spark plug wire, #2, didn't have a wire coming out of insulation and bent over the clip. So I fixed that.

I ran the engine and sounded more like normal, but after using a 7" sickle mower to trim under the fence for maybe 30-40 minutes, so "chugging" returned under lower idle. I went to finish mowing out a field drive and the problem worsened-loss of power, darker smoke out of the muffler, "chugging" along, limping back home.

This morning I took out the new spark plugs and they are coated with a light film of dry, black soot just the same as what is at the end of the muffler.

I am thinking the worse here but I was hoping someone may have more thoughts as to what is wrong with my 574. I bought my trator 4 years ago, 3240 hrs, light duty work for me, ran like a top. Thank you for thoughts and ideas!

May need the float in carb adjusted. could be a flooding issue.

I agree with GeorgeKY, the Air filter could be dirty or hoses to the carb intake could be collapsing (internally). Both would cause rich conditions you describe. Float sinking from a leak allowing fuel to "waterlog" the float. Jim

Kirk, could be multiple problems here. The gas tanks on these are getting rusty now, scale and rust will collect in the bottom halves, some will plug the screen [under tank] some will get through and plug another screen on the fitting right where it goes into the carb - Some will still get through that one and cause the float in the carb to stick. Ignition system on these gassers is points and condenser, that may need some attention [cap and wires too] On mine, at about 1500 hours, it was running so bad it was tough to get started. Turned out to be the valve lash adjustment, and at 1900 hours now, it's still running fine.