Just wondering has anyone successfully run a OS La .46 inverted and if so how did you do it. I have one that runs great upright or 90 degrees but inverted, no way. It will run at 1/3 to full throttle ok, but never idle and then accelerate. If the idle goes below 4500 and then throttle up it will die. I have removed it from a new plane for this problem.
Just curious, did you remove and remount the engine in all three positions on the plane in question or did you just hold the plane in different positions? It could be the level of the fuel tank in regards to the carb. As mentioned already, it could be too rich on the low end when inverted.