I have a 2004 Harley Fatboy I actually just bought it today the only thing so far that I found wrong with that is that when I stopped to fill up the tank the low fuel light doesn't go off and the gas gauge that's in the speedometer not on a tank lid doesn't show anything empty or full. Any help would be greatly appreciated as I am just learning and so far having a great time doing it thanks.

 

Sounds like the fuel sender unit isn't working properly or it's not making a connection somewhere. They are very simple design. Just a potentiometer really. If you are handy with an ohm-meter, you can troubleshoot it. If not, bring it somewhere to get it repaired.

 

I am somewhat handy mechanic wise and I do know how to use an ohmmeter can you just tell me where that would be located and just somewhat what to do I'm not very familiar with bikes yet as I just bought this one and I am learning thank you

 

First, make sure the sending unit is plugged in. That is under the tank on the primary side. Look under there near the horn and you'll see a little tube with a couple wires coming out of it. That should be plugged into the wire harness running along the frame.
Get a Harley service manual, not the Clymer one. It'll be the best $60 you spend on your bike.
It also sounds like you have an aftermarket speedometer.

 

You will need a manual like QC says. The best $$ spent if you want to learn your bike. I'm only familiar with newer softails so I can't really help much with the specifics of your bike.