You get a lot of negative stuff here, some from me. Here is something positive.

I have had some problems recently with new YS engines. I put a new YS .63 S on the stand this morning. What a sweetheart. Runs like a Rolex. The new regulator is easier to adjust and I don't have to drill a hole in the top of my planes to get at it.

My favorite 4 stroke engine used to be the .63 FZ. I like this one better. I have heard all the rumors about the S being less of an engine so I was hesitant to get one. After it is broken in, I will tach it to compare with my FZs. If that is favorable, I will get another one.