New Exhaust now bike wont start

I just put an FMF Powercore 4 slip-on on my bike and now it wont start. I have a 2007 DRZ-250. When I first put the exhaust on the bike fired right up no probs. I came out 6hrs later and would not turn over. It just pops and then stops. I tried kick starting it, I tried rolling down a big hill and jumping it that way but no luck. I took the exhaust off and tried to start it and no good. Does anyone have any idea what would be the problem? Could it be a battery problem? Thanks for any help!

Yes almost a full tank of week old premium.