Try these things
Drill a couple of 3/8" holes toward back of air cleaner.
Move clip on top of throttle needle valve to top notch.
Try cleaning and setting your points to .020
Could be points need replacing. Also replace condenser at the same time.
Mix your premix in a gas container, not in your gas tank. 2.5 ounces to 1 gal of gas. Oil goes in can first, then gas.
Drain your gas tank of old gas, flush the tank, fill with new premix