yamaha tx500

Hello, I have a 1973 TX500. I spent the last couple of weeks getting the bike running. Today I went to start the bike and the starter wouldn't work. I was able to kick start it though. I start checking some voltages and found that there was only 11.4v on the battery. I disconnected the battery and still only had 11.4V. I jumped the battery with my car and the starter worked. I am assuming there wasn't enough voltage to turn the starter. Also it is a brand new battery. With the bike running I checked the battery voltage still only 11.4 volts at idle. Even when I reved the bike it only went up to 11.7 volts. It seems as though the charging system isn't working. Please help. I'm not sure where to look. Thank you