If you havnt already solved the problem, give us more details like exactly what happened .
If you were flying how long did it fly before it knocked out.
It sounds like a typical lean setting on the high speed needle valve, it is possible to set your engine on the ground hold th nose up at full throttle and all seems right , shortly after, the engine starts lagging, loosing power, and it just seems like it lost a lot of power .
I would refil the fuel tank to about 1/3 of a tank, start the engine, set the high speed needle valve, hold the nose up at approx. 45deg angle and wait a few seconds if the engine stays strong and does not change shut it down refil the tank and off you go again. Hope this helps good luck