I made a conversion for replacing the old Yamaha headlight to LED headlight. It works GREAT on CT's, DT's, and RT's.
Search my old posts.

I was going to make conversion kits but I am getting away from vintage Yamaha things

I installed the Vape 12v system on my 76 DT400 and love it.  I had a hard time finding a battery to fit, I took a chance on a battery from Amazon (link below), and it's worked great so far.  Hope this helps!

12v battery

Because I can’t make up my mind, I now have two growing collections of parts. All stock setup or LEDs and try the 12 volt route. 
I really appreciate all the options and opinions. 
It’s going to be a few weeks before I can get the time to tinker around and see what I like. When that happens, I’ll check in with the results and any good stories of what I tried and what happened. Hopefully no stories about “Letting the smoke out!” 
Cheers. 
Pmb

If you look on ebay you might find a kit like this for Japanese wiring?

whereisbobl.com/tiger/smoke.html

 

Ha! Was no way I could read all that… Laffing so, off the rest room…
Sneezles61

Found a photo showing how bright the LED was.
If I had a more I would use them again, as they certainly make the bike more visible, it was simply the mechanical failure that caused me to swap it out.
My CT1-B now has a pattern DT175MX headlamp unit form Yambits, which has a replaceable filament bulb, this also works fine.
Both bikes have a voltage regulator fitted, which is an upgrade I'd certainly recommend.
Best of luck with whatever you do.

Rt1-pete, I do wonder if they have a rectifier built into them.  I'm sticking to my guns on the leds, only way they work right is with a rectifier.

An added rectifier, not the one that is your led light.  To clarify.

This might have been said before but an LED is a "rectifier". 

But most are not designed to handle the power of "rectifying" the AC to DC in this situation so they can burn up.

Rectifier= diode.  Led= light emitting "diode."  Alright I gave er my best, I'm leaving it be now, lol