Agree it sounds like carburetor. May be float bad or float valve leaking. Is this a tractor you have had a while? Has it always run rough? Has it been tuned up lately? I don't recommend Champion plugs in these engines. Have not had good luck with those. I usually use Autolite with good results. If still using points, try napa points and condensor. They are superior to what Deere sells these days.