Can anyone suggest what might be the problem. I hooked up a 12 volt battery by mistake to my 1971 honda SL100 and now the lights don't work, bulbs are tested and work and fine. Bulbs are tested and work, neutral light very dim, if i disconnect the battery natural light is fine.

 

Doubling the voltage (12 versus 6 volts) essentially doubles the current
So, the first thing to do is check all the fuses