this is a wierd 1

As I said this is a wierd 1. for some reason when I have my lights on dipped of full beam it will rev up to about 3000revs and stay there.
The electrics are in a bit of a mess think the person who did the  16v conversion wasnt the best sparky. When the side lights are just on it doesnt rev up and  sometimes it is all ok and theres no problem Any ideas  :dontknow: