Hi and thank you for your question.
In the interest of accuracy on my part, you say you changed the starter, relay and battery. Did you change those components with brand new parts? Also, was the battery fully charged before being put into service on this bike? Just to leave no stone un-turned, If the parts are not new, are they the exact parts designed to be used on this year make and model? I apologize for needing such detail, but in this forum, it saves us time to make sure I understand exactly what you did.
Beyond that, It sounds like the voltage from the battery is not making it to the starter motor. I would like you to put a test light on either the starter cable coming out of the solenoid or at the starter motor, whichever is easiest for you, and see if you can read battery voltage when the key is on, stop switch is on and starter button is depressed(simulating a normal start procedure).
The click you hear is the starter relay, also known as a solenoid. That is a good thing that you hear that. Now we have to figure out why nothing is happening after that.
Also, how long has this problem been going on? Is the scenario that it was running and starting fine one day then the next it would no longer start? Or did it start fine the last time it ran then sat unused for a period of time and have this problem show up when trying to restart? If there are any other pertinent details please fill me in on everything you think might be remotely associated.