Motorcycle Repair: 1981 HD FLT charging problem

Question
I am having trouble with identifying a charging problem. I am not a parts replacer so I try to identify the problem before I replace the part.  I will tell you that the battery was replaced recently because of the problem I am having.  The battery is not charging when I turn on my lights which I run at all times for saftety. I don't have any specialty lights, everything is stock. I can turn off my lights and the battery charges normal around 13.5 give or take. So do you have any suggestions as to why this would happen.  Thank You

Answer
Battery should have a full charge.  Then unplug the regulator from the stator,  put volt meter on A.C. volts. Start bike and see if your getting A.C. voltage.  At idle you should get about 20 A.C. voltage at 2k you should get about 40 volts. If good then shut bike off and plug in regulator.  Start bike and check D.C. voltage at battery Idle about 13.8 D.C.volts at about 2k you should get about 14.1 volts. If all good charging system is good. Then Do a load test on new battery.  If good you have something pulling volts when in is off. Maybe Rev bike to 2k and see what your D.C. voltage is