Perhaps your carb is now running lean and your are getting "spitting". My carb just picked up that habit. It will run better (stops spitting and noticeable improvement in smoothness and power) if you close the choke partially.
The carb is on the workbench at the moment. I found that the main metering jet was partially plugged and cleaned it with a welding tip cleaner. Blowing air through it was not sufficient.
Try running at about 1500 to 2000 rpm. Pull the choke knob. Does it smooth out?
