One thing to consider for a harley is that it operates at a much lower rpm, and as it's a 4 stoke, the intake duration is depending on the cam somewhere over 200 degrees every other crank rotation vs. ~120 degree duration for every crank rotation for a two stroke. Also the inlet tract on the Harley is much longer than a saw. Not to bash harleys, but their engines are anything but state of the art when it comes to producing top hp per cc or ci.
As far as I'm concerned, the theory that a rough port helps atomize gasses is bs. You need to understand fluid mechanics and that the flow next to the wall of a port is zero and velocity is max at the approximate center of a the port. Here's a display of boundry layer flow.
The only thing that atomizes the fuel is the carburator, or fuel injection. If you have a carb that just dribbles out the fuel, a rough cast port isn't going to fix that.
All high performance two strokes I'm familiar with have the ports smoothed out in the process of matching the ports and otherwise cleaning them up, and all make power gains in the process, albeit small gains.
My understanding of the keep the ports rough train of thought is that for lower rpm engines with long inlet tracts it helps keep the fuel from dropping out of the air flow, it has nothing to do with atomizing the fuel. But few engine builders have a background in fluid mechanics and hence truly understand air flow and merely pass on the lore they've heard.
opcorn:
