So there are known problems with the 46LA running inverted.

When you say drill it out, are you putting the same screw back in? As you said in yor post, I have backed the screw out as far as I can and it still acts the same.. To me it seems that the engine just does not like being inverted. However, as others have said, I have not put enough time on it either. I typically use the FX engines and have good luck with them. I just didnt want to try and shove a 46ABL in the front of the plane. Seemed a bit much. The LA engines I have ran upright have been just fine and very reliable. This inverted one seems to be a real pain.

Ryan