Interesting thread! I have a new OS46AX that I'm having the same issue with. My instructor can run it inverted and all wacky attitudes when the tank is 1/2 full or above, once he hands it to me and it gets to 1/3 tank it usually dies after either a dive or sharp bank. We have adjusted the low end several times, we are running on the rich side on the high end needle, engine is not hot when we checked it after the dead sticks or when landed before dying. We are checking for air leaks everywhere, tank, lines, pressure nipple, etc. I had the pressure line brass tube up tight against the tank bubble (sullivan 10 oz) so I bent it down a bit. He is thinking I may be having a tank pressure problem when the fuel gets low. I'll fly again on Sunday and report back if this helped.

If the clunk is not moving forward during a dive and is starving the engine, how do you correct this? Do you make the brass carb tube shorter allowing the fuel line/clunk to flex more and bend forward?

Odd that we both have fairly new OS AX engines and are having the same problem, I'll be following your efforts to resolve this as well. Good luck!

DG