You can test the regulator by putting a wire bridge between the two connectors of the voltage regulator plug. The plug looks like a T or a pyramid, depending on how you hold it. Connect the lower two when the plug looks like a pyramid. With the bridge in place, start the engine and see if the voltage goes up with the RPM. If it does, the rotor and other parts work. If the voltage stays stable with the plug in the voltage regulator as you vary the RPM, the regulator works.
Since you have a dead rotor, there is nothing you can do except change the rotor.
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Kevin
http://www.nohorizons.net