I recently purchased a classic motorcycle, it's current factory electrics are designed to run at 6 volts.
I do have plans to change it later to 12 volts but due to regulations in my country and to have the paperwork first in order I will have to prove that the engine fires and that the various electrics work (lights, horn, etc...).
I did not want to purchase a separate 6 volt battery as I have 12 volt batteries lying around so I decided to purchase a buck adapter - specifically this one.
Basically my question is if I do manage to start the motorcycle then is it okay if the dynamo/generator will also start outputting current? As I understand then the dynamo would be outputting around 7+ volts.
EDIT: I do not plan on charging the 12 volt battery. It's more of a temporary solution to show to the local department of motor vehicles to set the paperwork in order to register the motorcycle to my name and to get new papers for the motorcycle. What I was meaning by the question is if the dynamo starts outputting current then will the buck converter be safe (not fry/burn out).