I have a YS91AC (the forerunner to the FZ) This thing ran straight out of the box on 15% Cool Power. I adjusted the needle valve slightly rich for the first 4 or 5 tanks, then brought it to just under peak, and I haven't touched a thing on that engine ever since. Here are some videos of it in action on my Skybolt. The Skybolt is a heavy plane for it's size (90-120 4-stroke) I haven't weighed it lately, as it is about 10 years old (so add the extra weight of all the repairs and oil-soaked wood) plus, to add to the weight, it has a smoke system.

You tell me if this is a sweet engine!

Videos are here:
http://12.31.143.32
Note: on the last video, the engine sounds sick. This is an audio problem with the tape and NOT how the engine really sounds.