Just solved the issue on my rev counter, hope can help anyone with same kind of problem. I opened the rev and and found that one of the 3 weights in the arm of the needle was out of the place. Even before open it, when shaking there was a noise like a small piece inside that was free. If you have the same problem, be aware of not lost it when opening . You must be very carefull as the weight is about 1,5mm diameter by 3-4mm long. I profit having the rev opened to paint the needle. Looks and works like new.