Did you ever find out the answer? I am having the same issue
I have an '85 Yamaha CA 50 scooter. Trying to find replacement battery. When I search for it, I come up with conflicting information as to whether it is a 12v or 6v system. I have read that it is a 6volt system; however, replacement battery listings say "direct replacement 12 volt battery". Can anyone shed any light on this?