Harley-Davidson uses a common crank pin, meaning that both pistons travel up and down together at the same time. So all the weight is being thrown back and forth causing vibrations and the very particular “proprietary” sound or rumble.
The Twin Cam engine has a chain driven counter balancer creating less vibrations. As far as I know, the only other 45-deg. V-Twin bike to use a common crank pin is the Honda Shadow Ace American edition in an attempt to attract buyers by copying the Harley sound…and vibrations.