The light flickering. It varies depending on the type and specific voltage regulator to some degree.
Everyone suggests checking your wire connectors. Check the wires themselves too! The wires get cooked and don't work right anymore. Usually it is within an inch or two of the terminal. If the wire is hard, it needs changing. The B+ wire gets overheated on a regular basis and usually needs to be changed every 30k miles or so. BMW's aux. grounding wires do too. I see that mess cause trouble on a semi-regular basis. I highly recommend bolting a ground to your diode board and running it to the front starter mount on the case. Keep your hot wires away from ground wires and sharp edges as much as possible. I recently saw a picture and the B+ wire was all over the place. Wrong! Short and to the point!
With a voltage meter at the battery I have never seen an airhead with a stock regulator read over 13.9 volts. Many a guru says that if if isn't charging at least 14 volts something is wrong. That will get you a lot of business! If you are running a wet cell battery you don't want your charging system to be charging over 13.9 anyway or it will cook your wet cell dry in no time. It should be charging between 13.7 and 13.9 if all is well with a stock system.