My genny was 40 yrs old Onan. It began to have small issues then larger and larger issues. I bought all kinds of spare parts whenever I saw them to hoard up. My genny was obsolete, hard to get parts for and no one to work on it. I could not trash a good electrical end just because the diesel end had problems, BUT , the inevitable came true. I kept throwing money at a loser. Replaced it with a K.I.S.S. type and never looked back. New one, after about 250 hours, is more quiet, smoother and , so far, very reliable. If it's is 60 yrs old, might bed time to come into this century.
I hear you but these old ones are over the top on quality. Found the selenium rectifier has failed replacing it with silicon bridge tomorrow. It was the problem taking out the compounding transformer.