...to unasked questions.
From the Airheads forum. I finally got some answers to my questions and our favorite make of motorcycle.
This info is from the Snowman so it's likely gospel. [smiley=thumbup.gif]
Airheads are usually taken to be any BMW boxer engined motorcycle produced from December 1969, when the /5 came out, to the end of civilian production in 1995. The "Oilheads" are distinctly not in this group. Earlier versions of BMW boxer twins are not taken to be Airheads. Also, the BMW single cylinder motorcycles are not Airheads, as in common usage.
 Airhead is a sub-set, as are oilheads (R1100 & R1150), hexheads (R1200 except R1200C), chromeheads (R1200C), bricks (K75/100/100s) and whatever.
 The "head" part was used as a similarity to the nicknames of various Harley-Davidson engine types, ie: knucklehead, panhead, flathead, which described the actual shape of the cylinder head.
There ya go! Â Monte