Tried to run my first YS this weekend, I did not succeed. In my 20jr experience have had all brands of engines 2 and 4 stroke that gave me no trouble.
So I thought tha a YS would not beat me but it did. My conclusion (based on only two hours fiddling) is that it might be a superior engine but also can cause more trouble than any other engine.
If you just want to fly but do not need the best, go for another brand.