autobatch

You can check the regulator with a voltmeter (it should be under about 14v I think) but that is probably not the problem. It is more likely from what you have said, that the spark plug is fouling. Look at the plug. If it is all black and sooty looking, it is running too rich. If it is idling too rich, just adjust the idle mixture screw (not the idle speed setting but the low speed mixture setting). You might simply try turning it in (clockwise) 1/2 turn. You may have to clean the plug or get another new one to get it started. You can do a rough cleaning job on the plug with a wire brush. If the plug fouls (all black and sooty) after running under power then the main jet is set incorrectly. You have to take the top of the carbie and remove the circlip that holds the needle and place it one notch further away from the pointy end. This makes it run leaner under power (less black soot on the plug). If you make it too lean, that is no good either. If it is too lean, it will cough and sputter when you crank on the power even after it has warmed up.