I have an old MTD Trail Flite, with a Tecumseh H-35. Hasn’t been run since 1981. Has been stored in my basement, out of the weather. Engine turns freely still. It was running great when I parked it, A litttle cleaning, oiling, and maybe a tune up will do. I have a question though. I plan on draining and refilling the oil. After all these years, I expect some sludge or deposits to not drain out completely. What could I use to flush out the crankcase of all old oil and dirt, that will wash away clean without leaving any residue that could contaminate the new oil ? Is Kerosene okay ? I was thinking maybe refill, run for a short time, and then re-change the oil. Thoughts ?