RE: 50cc engine fine tuning
Here are the basic steps when the engine is warm.
#1 set High for peak and back off a couple of hundred rpm.
#2 set Low for good idle and transition.
#3 Re-set High as in #1.
Low affects High so every time you change the low re-set the High. That is it, not really much to it. I have used these simple steps now for many years.
Ralph