I am not very expected in motorcycles, but I think that the problem you have if it is the alternator anyway is easy to check with a tester if you have it but you have it which electric may help you only have to connect it to battery and check LKA load that this shows, there is a manual way to check if the alternator is loading correctly widely used in imagine cars that in the same way you can try on your motorcycle, you Dessconects a terminal of the battery with the motorcycle, if it stops the alternator is the problem, then it will only be to find out that part of the one in poor condition, and that the motorcycles alternators work differently because in an exentric oak turning inside a support, but it serves as GIA takes my advice.