Whats up all.

I have a 2003 600RR and for some reason the bike will not start when it is warm. It acts like the battery is dead and I can push start it with no problems. If it sits for a couple of days it starts with no problem. You would think if the battery was not holding a charge it would not start when it was cold either and would start after running into the store due to the fact the bike has been running long enough to charge the battery.
Just want to get oppinnions before i go drop 100 bucks on a battery for nothing. Thanks