By bille6: .... So the red tach indicator still lights when the brake is used.
Assuming you mean the Stop Lamp. I believe that's normal >> my 1981 KZ650-CSR has that feature. The Stop Lamp lets you know the brake light is working. On my bike if the Stop Lamp flashes without applying the brakes, that means there's a problem with the brake light circuit, which could be as simple as a burned out brake light bulb.
Agree that is normal if the 'Reserve Lighting' box is connected and working correctly, although not sure about a 650 CSR
( speak of the devil, i had a '79 version of that ) but if you disconnect the box and want to retain the brake light "ON" indicator,
you'll need to include the green/white wire. If not, the STOP LAMP
will work fine but the "ON" function of the indicator won't.