perplexing electrical problem on kawasaki er5?

it sounds like the earth to the bulb holder for the rear light isnt good and the tail light is back feeding through the brake light element and therefore lighting the brake light up.just try giving the bulb a new earth to see if it solves it run a new clean bit of wire from the side of the bulb and onto a clean piece of metal on the frame or the earth side of the battery.

adam bike doctor
August 2010