[bandito2]

Could be any of a number of things causing the problem. Pilot screw could need adjusting,
could be an extra air leaking into the intake from a loose carburetor or damage to the carb
insulator or failing intake pipe O-ring.

Might be caused by weak spark, faulty ignition pulse generator, faulty ignition control module,
faulty SE(start enrichment) valve. Could be from overheating, but the coolant temperature
gauge should be indicating that.

Might even be because of a bad batch of gas (water in it, too much ethanol, dirty fuel)
Try running it with some seafoam for a while. Can't hurt to try that along with some fresh
gas.
BTW, I won't get gas from a place that just recently was filled from the fuel hauler. It tends
to stir up any of the stuff that had settled in the underground tanks.

So after that opening it up and getting back up to speed, do you still have low speed power
issues?