More than a generation, yes. 100 years? Probably not.
So much unknown. Competition with other survivors with guns, knives, the ability to poison your well when you aren't looking or burn your house down while you sleep... assuming NONE of those kinds of things EVER happen, then, yes, the happy cooperative commune that never murders each other over scarce resources could keep a basic tractor running for 30+ years. Throw in all those other challenges... just traveling to a supply depot to get a new spark plug could be risking your life.
Even the happy cooperative commune is going to need centuries of relative peace in order to reboot the supply chain to the point of making new spark plugs compatible with the old engine blocks - or new engine blocks when the old ones are too worn to rebuild.