Dear Ickleboggle:

Unfortunately inverted engines need some special TLC when it comes to low end. Some guys have no problems. Others, like myself, can never get the low end right. You need to lean up the low end a little at a time. The low end screw is located in the throttle arm nut where it connects to the carb. Start the plane and turn the low end screw in about 1/4 turn. Throttle up and down. You will find a point (hopefully) that will allow the engine to run inverted without stalling. I myself don't have the patience so I put an on board glow driver in all my planes with inverted engines. The on board glow keeps the glow plug lit at low rpm and allows a nice low idle without stalling.

Good luck.

Pat