seeing the user name " streetrod" i would venture to say that the person is riding a vrscr. if its a 1130cc motor the timing chains are looooooooooooonggg, and are a bit noisy, which by HD's standards is acceptable. also the throttle body being located under the airbox(thats where the gas tank is on air cooled motors) and transmits the sound of the engine up through the airbox, sounds like a muffled thumping, and when running topless it will be even more defined. maybe this helps and maybe it doesn't............................................what i do know is i like fish sammichs :thumb