2006 Yamaha R6 Won't Start

My first bike has been good to me the last couple months, but is now having problems firing up. The strange thing is that the battery reads fine on a voltmeter, yet hooking it up to a car battery with jumper cables fires it right up. Push starts work too. Is it just some weird battery issue that I can fix by just replacing it or does the good voltmeter reading indicate another problem?