I just put new bars on my bike and now it won't start. Everything else works i.e. lights, turn signal, horn. I used a multimeter and it showed my wiring is good. Is there any way to test a relay to see if it's bad? Or, does anybody know what could be causing this problem?

 

Does the relay click when you hit the start button? Could be relay. Do you have 12 volts to the small wire on the relay when you press the start button? If not you may have a pinch wire on the right side control. You can jump from one side of the relay to the other and see if its the starter.

 

Inside the relay there are also two big contacks that the small wires (to the solinoid) pulls in.
These are where the battery and ground voltages make contack. Very high amps here. Supposed to slam together very fast to minimise time of big spark. These can wear out. Some can be replaced just there.
You can find these ,"Starting Relays" all over the place. Big motors have them,
Using 12 volts can require a lot of amps 200-300 maybe to get the job done. Can weld with that.