The engine is brand new. We have run about 8 tanks of fuel. 3 in the the air. I did try setting the low after setting the high, with the same bad result. I just had reset the high end back to the starting point after trying everything else. My understanding is you need to set the high rich, then set the low, then set the high to a leaner setting. Then maybe go back the low again. They both kind of chase each other.