Motorcycle Repair: battery power, harley sportster, volt meter

Question
I have a 1996 Harley Sportster and we put a new battery in it and for some reason, the battery keeps losing its power.  Do you know anything we can check?

Answer
start the bike up and put a D.C.Volt meter to the battery terminal,   as the bike is running at a idle there should be about 12 volts going to the battery, as you raise the engine rpms to say 2,000 rpms the voltage shoud go up to about 13.5 volts, if there is no increase in voltage. you have either a bad regulator or stator,