He's not performing a Monty Python Skit

He is keeping you from getting a ticket.

As an oncoming bike there aren't a lot of ways to warn someone there is a cop ahead. You could flash your high-beams on and off, but it is easier just to use a hand signal. So if you are riding along and a biker coming at you is whacking himself in the head, chances are he is not performing a Monty Python Mister Gumbey "My Brain Hurts". 

He is warning you about a cop. 

Or he has a Mental Condition.


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