Is my alternator putting out too much

Hello all,
I have an 82 Full dress KZ1100A Shaft. I have owned this bike for a long time and it has seldom been riden the last many years. Of course, I need to fix a few leaks (alternator grommet, cam plugs, fork seal, and rear shaft drive). I purchased a new battery and had it running last night. In years past, my battery typically only lasts one season. My voltage at idle was 13.1 and climbed to around 15.3 Vdc. Any issues with over-charging from these levels?

Yes that is too high. It should never go above 14.5 or so.

It can be a bad regulator, or bad sense line voltage to the regulator.

The regulator has a brown wire. That is the voltage sense line for the regulator to sense the battery voltage. Using the battery ground as a reference, measure the voltage on the battery positive terminal and then the brown wire, while the bike is running/revving. If the brown wire is getting to 15v, then the regulator is bad. If the brown wire only gets to about 14 when the battery is over 15, then the circuit for the brown wire is losing voltage somewhere.

The most common location to lose voltage is at the fuse holders. Next is probably the ignition switch.