Pull the carb and clean/flush it well including all the needles. Use new o-rings when reassembling. Reset all needles to factory settings including the idle gap. Reinstall it. Verify that the linkages are set up right. Install a new glow plug. Start it and tune as normal.

Oh yeah, and tighten the slipper all the way down and back it off 1/8 - 1/4 turn. You may need to check the slipper friction material to be sure it's still good.