so my turn signal and reverse light work ,but no brake light.change bulb, same thing.check to make sure there is not a right and left side in fuse box,nope.other side works like a charm.no loose wires......i'm lost.damn lost

Few things come to mind that could be culprit here.

Bad connection in bulb socket,

Bad connection further back in wiring harness, which on the BRATs, there's a couple but I'm not real sure on yours.

Bad/broken contacts in turnsignal switch, providing yours has same bulb filament for TS/Brake

jims brat had all kinds of lights not working. we followed all the wiring and unplugged and cleaned the contacts, plugged them back in. by simply doing this everything works now