Motorcycle Repair: 6v to 12v Bulbs, volt bulbs, volt bulb

Question
Hey, I have a 1974 Dt250. I have just recently replaced the lighting coil, and
now I'm getting full charging power. I have a battery thats in it now, with only
half the acid in it. Whenever I use this battery my headlight gets super bright,
but doesn't blow regardless of rpm. When I put the one with correct the
correct amount of acid in it, the lights get really dim. I blew a turn signal light
6v due to overvoltaging, and so I put a 12 volt bulb in. The bulb didn't blow
but was still bright. The same thing also happened to the instrument cluster
lights. Would it be ok if I just used 12v lights instead of 6v? Just to verefy the
motorcycle is a 6 volt system right? Thanks for your help.

Answer
Matt,

the bike is 6 volt system but it's voltage output
is balanced by the load the various devices
put on the system. In other words, it takes
the power available and divides it between
the battery, headlights, taillight, instrument
cluster lights etc to balance the output properly.
The system needs everything working good to prevent
overcharging and bulb blowing.
Your idea of a few 12 volt bulbs may be okay as
it may keep the system in check if the
6 volts aren't doing the job. Worth a try
and cheaper than buying bulbs.
The headlight may blow unless you cut the
voltage down a bit with some experimenting.
Some electronic stores have zener diodes
which can cut the output down but
need to be put where they can get
cooling air. They run the extra current to ground
but get hot doing it.