31cc ryobi with glow plug adapter ,original zama carb, 10% glow fuel ,mixed 1/3 glow 2/3 premium gas, ( glow fuel is pretty old ) , runs with heat on but is surging to full rpm's and falling off then surging to full rpm's again; all across throttle setting, from idle to high speed. switched back to magneto ign. and runs fine ( very rich but no surgeing) in addition when on glow/gas wants to backfire and run backward sometimes resulting in prop hub kicking off :any suggestions????

P.S. I have been running this engine as a gas/oil with magneto and it performs well in this mode total time on engine is maybe 5 hrs.