H-D manual the rest are way too general.
The H-D has very good charging system diagnostics.
to check the electrical system you need a known good battery, other wise all the test results are skewed.
charge your battery with a real charger ( not a tender ) get it load tested at autozone.
If you get a jump and try running the bike with a dead battery, your charging system may be damaged as it works beyond capacity trying to charge the dead battery
if your battery passes, proceed. Other wise find a Deka battery dealer and get a new AGM battery.
from there you can test the stator output with a voltmeter, and check the regulator
there is an electrical tech board:
and here's a post: