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Well, Mike, why we bikers wave to each other?
It's kind of like this: The nodding you see from younger guys is a sort of way to toss their head back as if saying "Hey, look at me. I'm pretty cool on this bike. What do you think?" While the proper response from the other bike is to throw their head back while saying: "Yeah, Bro, you lookin' cool!"
Now if it's some chick that looks like she's nodding, well, actually she's just trying to throw her hair back from in front of her eyes as the wind blows up and around a windshield and back towards the front of one's head. If the other party of the affected pair at the time notices this gesture of femininity, and is a male of normal persuasion, then he will nod back saying, in effect: "Hey, Babe, you is lookin' real good!" On the other hand, should the other party of the affected pair be of the same sex as the winsome chick, then her nod means something to the effect of: "You (rhymes with Bro), get on down the road or I'll throw your head back!"
If the nod is first coming from an older senior type person, then this is normally recognized as an attempt to stay awake by the party of the first part. Hopefully the rapid movement of the head will stimulate the blood vessels in the eyelids and help rejuvenate them. The proper response then, which is transmitted by a condescending nod, is: "Hey, you old fart, I'm glad you're going the other way."
Now as to the hand down to the side, that's easy to explain. As when we first start up our bikes using some choke, we occasionally forget to push the choke back in right away. In a friendly manner, we therefore try to remind passing bikes that they should reach down there in the area of the hand and check to make sure the choke is fully off. This is good as it keeps the bike from getting too much carbon in the engine's combustion chamber--but then that's getting technical, so I'll not get into that. I want to make sure I stay with the brief important facts. The other rider will usually also reach down there where the choke is to say (almost as if it were a form of sign language shared only by compatriots on bikes, so to speak) something like: "Oh, thanks for reminding me to check my choke to be sure it's all the way in so I don't get too much carboning up inside my engine."
Anyway, Mike, do you have a question?
RonK .
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