I can't believe I'm joining in, but
...the past three summers' trips; Chicago to San Fran, LA and back, and Chicago to Int'l Falls, and down to the Dragon, the Harley people waved or acknowledged me in some sort of friendly way [I]far [/I]more than the BMW riders. In fact two BMW people on a bench at a gas station near the Dragon/ Cherahola just about choked on "hello" when I sat down nearby and complimented their machine. Weirdos, and unusual for certain, but I'm just sayin'
BUT! I thought tap to the head was "something's amiss w your headlight" MSF basic.
I usually lean off to the left and do the low palm down repeatedly gesture for "cop ahead in your lane."