Now take the whole fuel pump assembly back to the bike. Place a towel between the two frame members and sit the assembly on the towel. Disconnect the electrical connector that is just above the fuel pump so the fuel pump isn’t running while you are making the adjustment. Now reconnect the electrical connector to the bottom of the fuel pump assembly. And so you wont run down your battery remove the 20 amp fuse for the headlights.
Take the negative lead of your digital voltmeter and attach it to a known good ground [NOTE: the frame on the Rockets are NOT intentionally grounded[ to ground it. Now attach the positive lead to the white wire of the four wire connector. See the pictures below. Go ahead and turn the bike’s ignition switch on. You should see that the voltmeter is reading 2.5- 2.8 or so volts. If you don’t, check that you have the voltmeter set properly and that the leads have a good contact to the frame and the white wire. If your voltmeter is reading a voltage, raise and lower the fuel level float. You’ll see that the higher the float is raised the lower the voltage output will be. If you have a fuel gage on your bike you’ll also see that the fuel gage will slowly move up and down as the fuel level float is raised and lowered.
What you want to do now is find out what voltage is required from the sending unit to trigger the low fuel light to come on. Lower the float until the reading on your voltmeter is 2.0 volts. Place a screwdriver or some other object under the float so the voltage will stay at 2.0 volts and let it sit there a minute. Then slowly lower the float bit by bit until the low fuel light comes on. This is a bit of trial and error but very important if you want to get it right. On my bike I discovered that the low fuel light would come on when the voltage was at 2.3 volts but it doesn’t come on instantly upon reading 2.3 volts. It takes a little while, maybe 30-60 seconds. I would suggest you find the voltage that will cause the low fuel light to come on then turn the ignition off and then back on again. If the low fuel light is now off let it sit a couple of minutes with the ignition on. If it still remains off you need to lower it just a tad and let it sit for a minute or so, keep doing this until the light comes on.
Once you know the accurate voltage that will cause the low fuel light to go on it is a simple matter of bending the wire that is attached to the float so that the voltage reading that will cause the low fuel light to come on, wont read that voltage until the float is resting about 3/16 of an inch above the black fuel pump assembly seal. The reason you want that 3/16 inch gap between the seal and the float is to compensate for the thickness of the tank which has a raised lip where the fuel pump assembly mates to the tank. If you fail to take this gap into account you might have a low fuel light that will never come on. Take a look at the below picture, as the unit comes from the factory the float arm, the silver wire that connects the float to the sending unit, is straight as can be. As you can see in the picture my recalibrated arm is just slightly bent. A little bit of bending goes a long way in adjusting the sending units voltage output.
Once you have made your adjustment disconnect the four wire connector from the bottom of the fuel pump assembly and reconnect the electrical 2 wire connector for the fuel pump. Remove the old fuel pump assembly seal and install the new one. Once again a word of caution, when you go to install the pump assembly into the tank be careful with the fuel level float. You have to turn the assembly at an angle then gently force the float into the tank. Also notice that the fuel pump assembly angles off to one side, if you try to stick it in going down the center of the tank you are going to break something expensive.
Once you have the assembly in the tank put the 9 washers on the 9 studs followed by the 9 nuts. Tighten down the 9 nuts using a torque wrench set at 5 NM using a crisscross pattern. Now remount the tank on the bike and install the fuel hose using the 2 new aluminum crush washers. Torque the banjo bolt to 15 NM using a 18mm socket. If you don’t have a 18mm socket a ¾ inch socket will do. Reconnect the 4 wire connector on the bottom of the fuel pump assembly. Reconect the two thin hoses to the bottom of the tank and bolt the hose bracket to the tank. Lower the fuel tank and bolt it down. Reinstall the 20 amp headlight fuse. If the tank was completely emptied add 1 gallon of gas so when you turn the ignition on the fuel pump isn’t running without fuel.
Now the moment of truth, turn the ignition on, hopefully the low fuel light is on. If it isn’t let the bike sit a minute or so with the ignition on. If it still isn’t coming on you got a problem. Your choice is to take it all apart again and start over or you might be able to stick something through the filler neck and bend the float slightly up.