[Al Skierkiewicz]

I have always been of the opinion that if the mechanicals are making noise they are trying to talk to you. I would listen and try to determine the problem. It might just be that at speed a part of the mechanism is hitting another part as in something is just slightly out of alignment. Look for wear spots on your rotating parts. Could be that the sprockets are not parallel and in the same plane. The chain would make a distinctive knock each time a sprocket tooth attempts to engage a chain link. The faster the speed the more (and louder) the knocks.