To be honest, Frank. I just bought the proper 6v battery the other day, I got it home and realized that my motorcycle battery charger only charges 12V batteries - so now I am waiting for a 6V charger that I bought off eBay.
The bike came with a dead 12V battery installed - and you tipped me off that the 1157 12V bulbs are often mistakingly in the tail lights, which was the case in my bike. So my goal now is to make sure I have all the proper bulbs in the bike, while I am waiting for my 6V trickle charger.
I did pick up the 1154 you suggested for the tail,...but it was in a generic package that claimed it to be a 12V bulb. Do you think that is a misprint on the package? Or can you get an 1154 in both a 12V and a 6V format? I was under the impression that all 1154's were 6V.