RE: DL-50 engine
While attending college, I relied upon a very used Yamaha RD-350 for transportation (motorcycle, two-stroke, two cylinder). Not having any money, other than the VA stipend, I couldn't afford to run the proscribed Yamalube oil injection lubricant. Soooo, I reverted to burning straight SAE 30 weight non detergent bargain oil. Worked like a charm.
Years later I found out that that was the standard oil for that bike in many countries of the world whose citizens could not afford the ridiculously priced Yamalube. Never had a problem with the bike for the two years that I owned it, with lots of miles accrued. It was still running great with good compression when I sold it to another student.
Ed Cregger