YOu may want to try a cut off loop,  see if it works for you, If not  try another  uniflow tank, many times it will  go richer  when at the end of the run

Randy

Tank is 1" deep by 1 7/8" by 3 3/4" tin open uniflow, pinch corner, back corner kicked out 1/8". Cutoff loop does work if I wait until it jumps on the lean, lean step. Engine is upright mounted Fox 35, PA-Fox needle, stuffer backplate, stick in bypass, stock head, tube muffler with 3/8" outlet. Current prop is cut top flite spoon 9 1/2 by 6.3 (10 x 6 cut). Fuel is Byron's 10% with castor and Klotz (50/50) added to get to 27% total oil. Engine has no binding, no rod or shaft slop. Plug is Enya No. 4. Pretty straight forward normal stuff.

Best,   DennisT

In my experience this is normal on an open vented tank, even uni-flo.  But usually when using uni-flo hooked up the tank goes a little rich for me.   Good warning to not do any maneuvers and get ready for landing.

Started looking at the setup and decided the one thing I did on this engine was to install the stick in the bypass. Pulled the backplate and found the stick had moved to the back side of the bypass. Since this is an upright engine the bypass is toward the circle center I decided to remove the stick. I don't think I will have any major problem with the burp and will see if the end of flight cut off is a little less screaming (I expect it to go lean once the Uniflow uncovers but not screaming). If this doesn't do anything (which could be the case) I will put a squirt of Armor all in the fuel to see if that cuts the foaming and give a cleaner cut.

Bests,     DennisT