your low end is to rich. When you engine is idling pinch the fuel line just before it hooks to the carb, if the RPMs increase your to rich. Close the low end needle just 1/8 of turn (the screw opposite the high end needle) and try it again. Keep doing this till the RPMs dont change and the engine quits then open it back up just a hair. Make sure your engine is broken in before you do this.