I have a DLE 30 in a Slick 540. The engine seems to run great upright or inverted. As soon as I push up from inverted flight, the engine stalls and it sounds like it was starved of fuel. The clunk line and other fuel lines are ok. I was told it was probably a lean low speed needle, but I didn't have time to try it yet. I have the low speed needle set so that the engine needs about 15 seconds of warm up before it will take throttle without bogging. I do have to use the choke to start more often than not. Spark plug (NGK CM-6) in a nice light brown color. That is the only time the engine gives me trouble, when I push up from inverted. Thanks in advance for any help.

Yes, it is too lean on the low speed needle. Open 1/8 turn and you should be good to go.

I would try opening it 1/16 turn. A little goes a long way on these Walbro carbs.

AV8TOR