The 74 was on oak's do not buy list. Frankly by now most issues are likely to have been sorted. The weakest link though was the transmission, I think it's why you see lots of used 74 transmissions out there. Folks have put a later one in their bikes.
Charging system gets a underserved Maintain it and it's do just fine. If you have to run aux. lights, heated vest etc. all at the same time, sure replace it. Otherwise just get to know it. BMW rotors do fail, often without warning. Rick Jones has a new rotor that I believe has yet to fail. I carry one as a spare. Stock BMw is stll fine after 65,000.
As with any bike, check it out and follow your gut.
"Between two explanations, choose the clearest; between two forms,
the most elementary; between two expressions, the shortest."
Between two motorcycles the simplest (DW)
Eugeni d' Ors (1881-1954); Spanish writer.