I fired up a new Moki .61 Long Stroke yesterday and had a problem. When reducing the throttle to about one third the fuel would suddenly flow back into the tank and the engine would quit. I discovered that the clip that keeps the needle valve from turning on its own had too big a hole in it. Air was leaking through the hole and into the banjo fitting that the fuel line attaches to. I found another clip with the perfect sized hole in it and put a gasket on each side of the banjo fitting. Today it will idle perfectly and turns a Graupner 12.5x5 wide blade at 11,700 RPM. Im mounted it on my BTE Venture 60.