could be running to rich try adjusting everything back to factory settings,
high speed needle turn the screw all the way down (clockwise) but don't tighten it. Then unscrew it 2 1/2 to 3 turns (Counter Clockwise).
low speed needle should be flush with the sleeve.
idle screw take off your air filter and make sure your throttle is at idle. then make sure that there is an opening in the carb..... i dont know just a thought, also try plugging in a new glow plug into the glow drive and make sure the plug is glowing orange