What is the reason your 1985 Honda Shadow is not charging the battery?

Answer 1

There may be several reasons for this. First, is your battery in good shape? If it is, then the problem is most likely a faulty voltage regulator, also called a rectifier. This is a recurring problem with older bikes. The rectifier cannot be repaired in any easy way and you should try to get a new one, or a second hand one from a motorcycle used spare parts dealer. I recommend getting a new one. When you have installed it, which is very easy, you should have someone in the know how measure the various electrical circuits of the bike with a multimeter to make sure there is no shorting to ground of any of the wire harness or connectors and repair any such if found faulty.