I picked this up last year for a Cub but haven't had the time to run it and mount it on the plane. Cylinder has good compression. Bearings feel smooth with no slop. When I first got it, I opened up the valve covers to take a look, and everything looks nice and clean inside there. Previous seller stated that it ran very smoothly with no issues. Sadly, I have not been able to test this. Engine has stayed indoors and on a shelf since I bought it. Kept clean and dry.