I can't say I know a lot about the customs and etiquette common amongst bikers. I'm not a biker myself and (to tell the truth) I've never been one - though I did ride a Lambretta for a couple of my late teenage years. So I found an article on the subject from Cycle World of interest. In fact I enjoyed it. I learned that you never ask someone if you can ride their bike (as in motorcycle). It's just not a thing you do:
Sharing is fine and good if it's French fries, bad advice or the warmth of a fire. But with girlfriends, cigars and motorcycles, no. That's biker law.
There's more: even touching someone else's bike is something you don't do unless you've been invited to. I was beginning to think there might be a sexual dimension to this, when I learned that there is. In any case, I'll be mighty careful now if I should find myself in the presence of a biker and his or her bike. (Via: RW.)