What is the "breather" on the rear brake? What does it do? I don't see anything in the owners manual about it.

 

Breather... a bleeder nipple is the only thing remotely close to looking like a breather. Maybe the previous owner left a piece of tubing on it from bleeding the caliper.

 

Yes that is it. I guess the reason I was calling it a breather is because when I was looking at Kawasaki Part house and the rear brake, when I clicked on what looked like the bleeder, it calls it a breather. Although I could be looking at the wrong thing.
Kawasaki 43056-1056 - BREATHER-BRAKE : Babbitts Kawasaki Partshouse

 

Bleeder... Japanese for it - lets it "breathe" brake fluid.