Please Help no brake lights

After connecting the positive battery cable  , the black wire (one of 3 wires in the triangular connector right by the battery)  (has a black red and yellow wire) .. burned and melted now I have no brake lights and when I touch the broken wires together it melts it even more

Start by locating the short, then clear it. You may have a wire shorted to ground. Take a meter and start at one end of the circuit and make your way to the other end looking for shorts to ground (frame). Dig up an electrical schematic for your bike.

You'll find one on this page that is useable:

https://www.thumpertalk.com/forums/topic/549103-wr250r-electrical-issue/


Good luck!