My 1979 stock CT70 has a vibration that has been annoying the heck of me for some time now. It appears to be coming from the head area and is most noticeable after rolling on the throttle and then decelerating to a cruise speed. Also very noticeable when decelerating to a stop. The bike idles and runs perfectly and there are no discernable knocks or anything like that. Is this be somewhat normal for these CT70s? Could this possibly be cam chain noise that can or can't be adjusted out?