Glowgeek

I have a vintage Champ tail dragger with a new fully run in os15la and It's giving me fits. I can't adjust the airbleed screw for idle with the tailwheel on the ground, it goes lean and dies. A richer adjustment makes it idle a little bit longer but then if I lift the tail wheel off the ground during idle the engine goes overly rich and dies. If I adjust the airbleed with the tail up it will idle forever but as soon as I drop the tail back down it goes lean and dies within 5 sec.

1. Idles perfect and forever on a level test bench with the same tank, lines, fuel etc but If I tilt my test bench up at more than a 15° angle it leans and dies within 5 seconds.
2. Back plate and carb have been sealed up with rtv.
3. Tank, fuel lines and high speed needle tested with pressure and vacuum, no leaks. Carb not tested for air leaks but does not appear to leak fuel.
4. All screws checked for tightness.
5. Compression is normal.
6. Tank centerline is level with carb spraybar on the test bench and aircraft.
7. Airbleed screw is screwed in just past halfway across the airbleed hole for good idle on test bench.
8. No bubbles in fuel lines.
9. Pressure nipple is clear and tank pressure at full throttle is a little over 1.0 psi.
10. Runs great at wot in any position.

I say no bubbles in fuel lines but there is a small bubble that forms right where the fuel line plugs into the carb after it dies from an overly lean condition when I tilt my bench up 15° from level.

I'm lost, never had this happen before but then this is my first .15 and my first airbleed carb. Maybe the carb is leaking in air where the black plastic fuel inlet connector meets the carb body?