It sounds like the rectifier is bad. My first thought would be to change that. Of course, that is after inspecting the plugs for proper connection and to make sure you don't have any loose wires between the retifier and the stator.

 

same thing happened to me. but dont do what i did. i replaced the rectifier first, and put it on. drove down the street for 5 mins and broke the new rectifier i just bought. turns out the stator fried after my rectifier had gone bad. i hadn't noticed a burnt plug.

i had to buy a new stator, and another rectifier. but after replacing both i have had no problems so far thank god.