1. Never have I heard the term "dink" used refer to catching a ride on a bike. Where is this term used in this way?

2. I have no idea of the derivation of the slang verb "to dink." It is most often used with the preposition "with" as in "don't dink with that" or the preposition "around" as in "are you just dinking around?" My sense of its meaning is to fiddle, to adjust, to play with, to tune, to mess with, to manipulate. Dinking with a radio is a way of changing the station received. Dunking with a carburetor is a way of getting it in tune with its companion carburetor. Come to think of it, dinking around with someone may mean to be fooling them, conning them, putting them on, leading them astray, playing with them, as in the usage "Are you serious or are you just dinking around with me?"