Bottom line..[8D]...The carb on a DA 50 was originally made for something else, probably a chainsaw...The manufacturer of the chainsaw had the carb metering holes calibrated for that particular engine...Apparently the hole in the carb that is controlled by the high speed needle is just large enough for that rpm and no larger, no matter how far the needle is screwed out....That's apparent by having to adjust the carb to 85% of the top rpm by using the low speed needle..It was not designed to be that way....I guarantee I could make the hole large enough to flow more fuel and richen up the mixture...I also think a WT499 from a Glow G23 would do just that, it has large enough fuel passages to flow at least twice the amount of gasoline needed for the G26, so much so that it also works with methanol with no other changes...