K-Tech Page Maintainer's Note: This will only work for early K-series bikes. Certainly those with the amber 7l light and the red 4l light, later ones up to the point where the analog sender was installed.
Purchase two 1 K OHM potentiometers from Radio Shack, #271-342, for $1.49 each. Splice one into the brown/white (4 liter) wire and the other one into the brown/black (7 liter) wire, where the wires go into the tank.
Measure 4 liters of fuel into an empty tank. Adjust the potentiometer for the red light so it comes on at the 4 liter content in the tank.
Obviously, the other potentiometer should be set so that the yellow light comes on at the 7 liter level. Of course, you could be creative and set them to come on at any level you desire.
Rather than empty the tank, I emptied almost all of it, then ran the bike until it ran out of gas, so I would have a true indication of liters remaining of useable capacity.
You can get as fancy or simple as you want with the installation. I mounted the pots in a small plastic box, with the adjustment screws accessible through two small holes drilled in the box. I also mounted a small switch through the box and wired it to be able to disconnect everything from the fuel lights just in case the fix didn't work. I spliced in enough wire to be able to mount the box to a frame member just behind the right side cover. I filled the box with silicone, completely covering the pots and switch, as protection from the elements and vibration.
This fix has worked flawlessly for sixteen years.