I'm running out of ideas for getting my BME50 to operate reliably, and I need some outside opinions. Here's the situation:

I've been running this engine for about 6 gal. now and have yet to get completely confident with it. Today I thought for sure the problem was solved, but I was wrong. First two flights the engine fired right up, idled smooth (as can be expected), transitioned instantly and made tons of power for both flights. Third time I fired it up it wouldn't come off idle without gagging and trying to quit. So I opened the low needle a little and everything was fine. Now I never changed the needles after the first two flights, so why should I need to now.

Here's the real trouble. Since I purchased the engine, it has behaved strangely like this. Sometimes changing the needle works sometimes not. So I started checking for other reasons. I checked the fuel tank and lines for dirt, bad fuel lines and looked for air bubbles when the engine was running. No problems. I checked the carb. filter (walbro), and flushed the entire carb with clean fuel. No problems. I checked the plug gap and electrode color. Everything as it should be. I checked the ignition battery, switch and related wiring. No problems. I even pulled the engine and ran it on the bench to see if vibration was causing problems. The engine ran perfectly fine on the bench, didn't take any fits. So I thought maybe I needed to mount the ignition box in a way that would reduce the vibration. Put the engine back on the plane, mounted the ignition module in new foam rubber and strapped it down good. Fired the plane up today and thought my worries were over, wrong. Third time I started it the problem returned. I'm at a loss, any advise would be very much appreciated!

Ben