I had a strange thing happen to me while flying in Peoria. On my second round flight things were going along just fine until the overhead eights. Suddenly the motor sagged/went rich, I nearly lost the plane but managed to save it by the skin of my teeth. The rich run continued till the lean out at the end of the tank. I'm running an OS 20fp in the BBTU set up. This has been a consistant and problem free performer. The practice an first round flights were trouble free. The only change I made was to use one eighth ounce less fuel to shorten the flight a bit. I have not had it back in the air yet, but have looked it over and can find no problems. I can think of a lot of things that would make it go lean, but not rich. The fuel I'm using is a 50/50 blend of Sig 5%-25 all castor and 10%Tower power(I know, but it's worked well all season so far) Any ideas of whats going on? I'll post a photo of the set up, the only change from the photo is the addition of a check valve between the muffler and tank. Thank you in advance for your help.
Bob