I was thinking it was a diesel. You may need to clean the carb, it could be gummed up with passages blocked. If you can get the "dip tank" type of carb cleaner and soak the parts, it should clean up.
I always liked those 1020s. Frankly I was disappointed when so many tractors went to diesel. Generally I prefer gas engines. Quiet, inexpensive, simple to work on....
If you like the way it has been running I'd suggest that you go with a new fuel filter before considering taking the carb off and cleaning it. That's not a difficult job, but there's enough details to it that it's not the sort of project I'd recommend for a neophyte mechanic.
Having said that, I do agree with Zebrafive that you may find the problem to be in the carburettor itself.
Every carb is basically two carbs in one body. There is an internal circuit for idling, and a completely separate internal circuit that feed gas for all RPM above an idle. They are called respectively: the idle circuit and the high speed circuit.
Generally the problem with all old gasoline engines is the same today. When gasoline gets old it could always form some crud - crud being dirt, sediments composed of particles falling out of solution, and long-chain hydrocarbons called "varnish". But modern gasolines form more crud than older gasolines, and the carbs that used to work fine get clogged today. That's not the whole story, but it's close enough.
Crud often settles to the bottom of the fuel reservoir or "float bowl" in the carb. Then the crud gets sucked up as gasoline is used and eventually clogs some of the smaller passages. It is in the idle circuit that you see problems with crud first - that's just because the inside passages (orfices and drillings) are smaller diameter. But apparently yours is showing symptoms in the regular or high speed circuit. If I were to guess, that's because the high speed circuit has a part called a "main jet" that hangs down near the bottom of the float bowl and is right there in the wrong position to suck up crud. Gasoline 30 years ago didn't have the problems with crud formation that modern pump gasoline (other than aviation gasoline) does.
But stick with it. Carbs are basically simple even if they can be exasperating. And sometimes they will just spontaneously clear themselves. Any of the many sorts of gasoline treatment added to the gas tank may/maynot help with this. I doubt if any of the additives would hurt.
BUT FIRST THINGS FIRST: Change the gasoline filter, clean out the gas tank if you can do so, and replace any rubber fuel lines between the tank and carb with modern ones that are impervious to the modern gasolines. You replace the rubber lines because the old 1970s vintage rubber fuel lines eventually get hard, crack, and leak (fire!) with today's gasoline. Gasoline that contains even a small % of alcohol - like so many pump gasolines do today - are particularly hard on vintage rubber parts.
Do those things and then just run it normally for a few months. Don't be surprised if it stutters and sputter a little - try to just stay with it. Lots of times they will clean themselves up inside.
Nice tractor, and worth some fiddlng. I'll bet once you get the fuel and carb going right it will work for you for another 50 years. My 530 did; and still does.
rScotty
