I have never seen a YS that needed an onboard glow to sustain a good idle, and your 140 shouldn't need one either. Do you use a filter on the fuel line? If no, you should. Does the idle improve if you leave the glow starter on? If yes, it is too rich. Remember, the regulator has very little effect on the engine at 2000 rpm. I would start by cleaning the regulator out. Your symptoms COULD be caused by debris in the regulator, considering how far you have the screw turned down.
Paul