Stan,
About mixed fuel for these engines----once you add oil to gas for the mixture, the octane is reduced somewhat & will continue to degrade quicker than unmixed---especially in colder weather, so it's not a bad idea to mix fresh gas every 4-6 weeks in warm weather & in half that time if you fly in cold weather. I've been flying ultralights for about 26 yrs & can tell you first hand this octane reduction of mixed (2) stroke fuel really does happen which is why I mix 5 or 10 gallons just prior to flying. Some UL pilots purchase Hi test gas to offset this condition. Also, I've found no problem w/ dumping a gallon or two of aging mixed fuel in my vehicles just to get rid of it . Losing 1k RPM to an old mixture when your rear is in the seat prompts you not to let it age too long.