The headlight getting dim at idle, and getting brighter with rpm to a point is typical with our stator systems. The way the voltage regulator and stator work in these is at idle, they are making low voltage, but still enough to illuminate the light. the voltage regulator isn't doing anything at this point. when you give it some rpm, the voltage regulator kicks in around 14 volts, and shunts the extra voltage that the stator makes to ground to give you a regulated 14 volts or so. the only purpose of the voltage regulator is to prevent the voltage from the stator from being too much and blowing out the headlight.
If you are having idle problems, i would ty to increase your idle speed a little to prevent it from wanting to die on you.
