I was pondering the whole issue I hear of every once in awhile about how people complain of heavy handlebar vibration. I only notice it when I'm slightly engageing the rear drum brake while throttling or stopped and pulling on the rear drum brake. This leads me to believe it is a vibration being fed to the handlebars through the rear brake cable. Perhaps the problem people complain of as heavy vibration could be related to having the rear brake drum adjustment to tight.