Flap wheel? Why are you sharpening your tungsten with something usually high in aluminum content i.e aluminum oxide? A harsh start can be from a sudden burst of gas. Increase preflow time. Also sounds like possible bad gas. 1/16 tungsten is WAY too small unless you are welding at something less than 20 amps, especially on aluminum. It will cause bad starts. I know what the "charts say" from the big guys, but they also recommend using pure tungsten too for aluminum.