GS 21R operating instructions say to start out at three turns out. That said, I run 15% Cool Power with a OS #8 and both needles 2.5 turns out. If the engine is cutting out and there is not a whole bunch of blue smoke, I would say you are running way too lean. Try my settings and give it a try. Remember, the GS 21R runs hotter than most and needs rich settings. ANd let it cool off before running again. Good luck.
Chris
Richmond, VA