Hi guys,

the following story could maybe bring some light to the vibration issue. Some days ago I had a crash. "Landing" was out of sight, damage was minor, but evidence showed that the plane has hit the -soft - ground nose first. After inspection, the engine was clean, I noticed that it was much harder to turn over by hand. Made a test run - vibrations were awfull. My SP was always a smooth performer, but now it was shaking like hell and rpms were poor.
A flying buddy, who was interested to see the inside of the engine since the day he saw it first installed in my plane, disassembled the engine, and before I could do something against it he took a piece of hard wood and a hammer, placed the hardwood onto the gear of the cylinder jacket, and applied two gentle hits.
Assembled again - the engine was easy to turn by hand. Fired it up - no vibrations, performance as ever.
I have no equipment to measure the play in the gear. But obviously its fundamental to engine behaviour. I do not know wether my buddy was just lucky to get it right, however there are certanly some tolerances. According to his opinion it is important that there is no play when you turn the prop, the starter screw has to turn instantaniously.

regards
Andi