First thing that comes to mind (as well as checking connections, especially in the headlamp) is to check fuses and relays as you might have inadvertently shorted and blown one of these in the process,
I also doubt the tank has anything to do with it unless you have instruments on the tank which i doubt you do.
If all else fails, pick one light, and follow the wire to (referring to wiring diagram) to source and check with voltmeter to determine where the power source starts (or stops depending on which way you are tracing)
Hope this gives you a few different options to consider.
