my 82' yamaha seca 400 is running rich. I had it running for about 5 minutes and it started to sputter, wouldn't take any throttle response and then it died. kept doing this every time i started it until now it just wont start. I pulled the plugs and they are black at the end. I assume this is running rich. I'm learning as I go on the mechanics of this bike so anyone know how to fix this problem? I though carb adjustment until i realized i have no idea how to adjust the carbs on it.