I just finished my first plane with a 4-stroke engine. I have a .40 size cub that I put an OS .52 4-stroke in it. I just started the engine for the first time today to break it in. It seems like the plane vibrates quite a bit. Is this normal? Am I going to have structural problems in the future? Is it just that the plane was running rich which causes the excess vibration? Should I switch over to a soft mount?

Thanks,
Jim