It's more likely to quit with a lean low needle than a rich one. If the low is really rich it could quit if it loads up with fuel at idle...but only if it's idling a long time and then the throttle is pushed to full. Did you do a full tune of both needles yet? For the low needle, let it idle for a while on the ground. If the RPM's go lower and lower until it sounds like it's about to quit, it's way too rich. If you let it idle for a while and the RPM's keep going higher, it's too lean. Once you get the idle RPM to stay the same test for transition. It should snap up as fast as possible. If it's slow to transition, richen it up just a tad until it's fast.

And if tuning won't solve it, you could have some air flow in the cowling that's disturbing the carb's mixing of air and fuel. Either air blowing on the metering diaphragm vent hole, or air blowing into the air inlet of the carb....or both.