Hi
I used to feel the same way as Jim regarding 4 strokes. Until i bought a plane with a YS 63 and all i can say is apart from the higher running costs it is the most predictable, reliable engine I have ever owned. If it quits in the air it is because it has run out of fuel. The only down side is that unless you are running it on 20% plus nitro you are wasting your time.

I would fit a YS 110 without a seconds thought.

Mike