Hello everybody! Hope you enjoy the easter days!

Being new to this thread I'd like to introduce myself briefly. I have been building an flying model airplanes for 36 years now, with the main interest in aerodynamic and structural design, i.e. building my own planes from scratch mostly. Because I am addicted to the "Golden Era of Air Racing" it was logical to let a long fostered dream come true and build a racer with a radial engine. Searching the internet for information about a suitable engine I stumbled over this thread and my impression was, that it is one of the rare useful ones with thorough information. This encouraged me to buy the EVO 999 recently and I am about to do my first break-in runs soon.

And here it comes: Yesterday, preparing the first run, I started adjusting the valve clearance. With the plugs removed I cranked the engine and was shocked to hear an unusual sound every eights rotation exactly at the same position. It is a clear "clonk" accompanied with a slight resistance while cranking. Now my question: Is this normal, did anyone of you experienced similar things?

Have a nice day! - Olaf