48 won't quit coughing

AS A GENERAL RULE, the occasional koff is NOT a carb adjust problem. Its ignition. And since you've seemed to isolated it to #4, replace the sparkie, $2 cheap. (lotta sparkie problems you can't see with naked eyeball)

There is always the possibility that #4 is having sticky valves, compression check can usually veryify that, but not always since you claim intermittant..... ....Dell

First, if you are using off-the-shelf plug wires from some auto store, they're probably resistance wires. This denegrades spark. You need to use good ol' copper core wires (no resistance).

Second, check distributor bushings for side-to-side and up n' down play. Excessive wear in bushings will cause point gap to be eccentric.

Third, check point gap/condition, your rotor, dist grounding strap and all electrical connections. Might even wanna put in a new coil in case it's going bad (a spare coil for front-mount distributors is a good idea anyway).

Fourth, especially with the #4 plug running a bit of soot, make sure you are using Autolite 437s or equivalent which are a "hotter" plug and less susceptible to fouling.

If you aren't getting a nice whitiesh/blue spark, you gotta run thru your tune-up items and get it before you can properly isolate other problems.

Yes, it is possible you are running rich but that does not cause sputtering you are describing.

If all of above fails you should perform a compression test (not a bad idea anyway if you replace your plugs) both dry then wet (takes 5 puffs to get a good reading) in order to evaluate rings and valves. Min compression is 90 lbs with no more than 15% variance between cylinders. These tractors will run with less compression, but an overhaul is nearby.

If ignition and compression are okay, then check for leaking manifold (common problem) and of course fuel screens (all 3). If above all check out THEN start messing with the carb. It could have crud in it, bad needle, float problem.

As for cam wear, very easy to check. Your rubbing block on your points does not cover the whole cam. Simply run your finger up n' down on the cam to feel for wear. Doubt it's appreciable (if you can feel any wear at all) AND on these low rpm engines it shouldn't make any difference.

As for your sputtering problem, you've eliminated some of the items, but until you check the rest, you won't know what the cause is.

Chigger ('50 sidemount) has a random sputter but I know it's the dist bushings fault (about 1/16th inch play). I just live with it because she does all I need her to.