Talked to Gerhard at Aircraft Aviation last week about my problem. He felt it is due to airflow over the carb inlet causing a vacuum. The carb keeps putting out the fuel it is supposed to but does not get enough air so it goes rich. He explained how to make a scoop to put over the inlet to force air into the carb. He was very helpful and spent a lot of time explaining it to me. The reason it goes rich when inverted or in knife edge is turbulence from the different aircraft angle. My rich takeoff runs are from the increased airflow over the carb as speed picks up.

Unfortunately I don't have room in the cowl of my Yak for a scoop. I'm going out this morning and am going to tape off more of the opening on my Yak55 to see if that will make a difference. I already have the top half of the cowl closed off with a carbon fiber plate. I'm going to tape off both sides even with the cylinder and see what happens. If it works I will build some permanent pieces to close it off.

Love those round cowls but they sure do let in a lot of air!