My motobecane SP50 from 1965 was the high performance top of the line model. It was fast. Like 40+ in the flats. The manufacturer reccomended oil ratio was 8oz of oil per gallon. This was before there was special oil for two strokes. Motobecanes from te seventies had almost the same engine, but used 4oz of oil per gallon. The oil got better, a little.
The engine isn't important, it's the oil that makes the difference. If you use a high quality synthetic oil, which you ought to, feel free to run 50:1 without a care. If you want to run lawn mower oil, i would mix it a bit richer.