Friend of mine had same issue. He changed batteries, starter relays, ran new wires, and still would have the same thing happen sometimes. He finally just put one of those push button deals on his starter. If it clicks when he hits the starter button on the handlebar, he just reaches down and hits the button on the starter. Starts every time.

 

Most of the auto parts stores and batteries plus stores have hand help battery testers that will load test a motorcycle battery. You might need to figure out the cranking amps or cold cranking amps if it isn't on the outside of the battery. It would save time and make for a more accurate test than someone guessing. I'd take the battery in for a test so you KNOW it's good or bad and then go from there. That same tester would also do a load test of the starter still in the bike if you can get access to the battery once it's back in. You'd want to check your connections to the starter and back are tight and clean but again if it showed an excessive draw, you'd know.

 

sounds like dirty contacts on switch on gas tank.