I realize a harley is different, but racket is racket, and how an engine is cooled shouldn't mean much (especially when in my experiment, the engine wasn't even warmed up yet). Harley's merely flow oil thru, at very little pressure. (4psi @ 2000 is normal on mine) Oil is pumped to the rockers, then it's pretty much splash-n-spray after that. And it's very apparent to me that the reason for all the racket I got, was because the splashed synthetic oil was NOT viscous enough to fill the spaces between the cam ends and bushings, cam gear teeth, piston-to-cylinder wall, rods-to-wrist pins, and all the roller bearings! IMO, racket=metal-to-metal.
I Understand the difference between the ball-bearing shaped molecules of normal oil, and the spagetti-shaped molecules of synthetic oil. I also understand that a synthetic oil molecule is nearly impossible to destroy, unlike a normal oil molecule. But until they figure out how to squeeze enough molecules between the moving parts of MY engines to keep them quiet, I ain't using it!