I have looked on line and searched the forum for a previous thread and I couldn’t find any information. 
Im thinking of upgrading my 69 DT1B to 12 volt and I am trying to find a 12 volt battery that will fit the battery box. It seems like that is a hard find. 
I am hoping someone here has done the same upgrade and knows of of a small 12 volt battery that will fit. 
Thanks 

Just measured my battery box quick, working with 2 7/8" length, and 2" width, if your lucky.  Closest thing I see in the yuasa book is a yb2.5l-c.  Slightly too big though both measurements.  Mind me asking how your converting the stator?

If the upgrade to 12v needs a battery, then the retailer of the upgrade might supply, or give details of, the replacement battery.

Yuasa NP1.2-12 fits.

www.amazon.com/Yuasa-NP1-2-12-Sealed-Bat...rminal/dp/B00FA61J54
 

As far as the stator mod goes, I am not sure if or how I will do that if it is even necessary. So far all I have done is measure the output of the green, yellow and white wires coming from the mag. I used an analog meter so I could see the voltage fluctuations better. Digital meters are too slow to see what is really happening. 

with the engine at idle I see 12-13 volts AC from the yellow wire to ground. With just a slight increase in RPM the voltage jumps to over 15 volts and climbs with more throttle. I have to do more measurements to determine how it reacts to different loads. However my battery was pretty dead before I started the bike. 

If the voltage holds up from LED headlight and taillight and battery charge loads then it should be fairly easy. After all, the purpose of the choke coil is to tame the voltage down to prevent it from blowing up 6 volt incandescent light bulbs. With a couple large diodes or even a 12 volt rectifier/regulator it should be possible to get enough voltage with the current mag/stator. 

Now it’s totally possible that I am missing something and that it won’t work. Maybe there are others out there that have tried and succeeded or failed. I searched the forum for previous threads but didn’t find anything. Maybe my search was not thorough enough…

If anyone has any experience with this topic I would love to hear about it. 

Thanks for the responses. 
 

Some have simply installed a 12v incandescent headlight and gauge lights and left the battery circuits 6v

I just looked at that Yuasa NP1.2-12 battery. 
it will fit but it would have to be on end to fit into the battery box. Will it work that way? I realize that it’s a sealed battery. I am curious if the battery fluid will spill down and leave the top cell partially dry. 

I think the problems charging are alot to blame on the single diode rectifiers. If you used a full bridge rectifier, you could utilize the full wave of the ac output. HOWEVER.. this will not work, unless you isolate your negative from the frame of the bike. The reason being is that the other side of the stator winding is attached to ground. You would need to rewind both lighting/power coils to do it right, and be able to isolate the ac side.

Also, depending on your setup, the green wire with red stripe I believe is the most output, yellow wire is slightly less, intended for the headlight.

Thanks for the tips everyone. I was thinking similar things to what Knutco11 said about the isolated negative. I am also considering what MarkT said about running 12volt bulbs and keeping the rest of it 6volts. Ultimately my goal is brighter lights. I tried a couple 6 volt LED bulbs and they were ok but not nearly as bright as I hoped they would be. I have a couple of 12 volt LED bulbs and I think I will try them. I still need to see how much of a voltage drop the choke coil creates. My understanding is that it will knock it down to around 8 ish volts. I may have to adjust it. More tests are required. Whatever I end up doing, I will post the results. 
Thanks again to everyone for your help and advice. 

Led lights are probably not the best answer for these old bikes. Unsure if know but you NEED DC power to operate an led light. By the time you rectify the power, even with a full bridge, you lose alot of power. I think the best upgrade would be 12 volt incandescent headlight like markt says. Keep the lighting circuit ac as much as possible. I believe the battery is required so if you break down on the side of the road, you still have a taillight. Blinkers and horn I suppose too if got them.