Couple years ago I picked up a fairly intact AT1 at the local swapmeet:

yamaha-enduros.com/index.php/forums/1968...t-the-swapmeet#88830

Since, I have torn the cycle down to some degree for cleaning and inspection. Having removed the starter dynamo yoke & armature, I noted a very degraded condition of the yoke, with brushes worn down to the nubs, corrosion and being quite grubby as well. The armature was also well worn and dirty. In digging thru my parts stash I recalled a "candy green" Yamaha 200 twin I had gotten on the cheap years earlier. What was there had been pretty decent, but not worth the effort IMHO to fool with, so parted the cycle out. I ended up keeping the yoke and armature because when I put them online to sell, I had no takers. Those components are in very nice shape. However, have recently compared the assemblies and find they are pretty close to being the same as the AT1...with the same parts numbers. There are some wiring differences, the point assembly and the cam, but I have a feeling much of it will exchange. Would be happy to hear if anyone has been in a similar situation and if this transplant is a feasible one...THX!

Sounds like a good plan.
I guess you'll be the first to try it & let us know. If it 'does' fit, then only one set of points will be used. Actually for a laugh to trick people you could run two plug coils & two plugs in the head & have it firing both. Not sure if you'd need two condensers. Actually you could do that with any AT1type battery ignition model, wonder someone's not tried it--two plugs--two coils etc. Might give a cleaner burn & could raise the compression then go faster into the sunset--then walk home with hole in the piston.

It would be interesting to see if it works...  I'd be surprised if part numbers of major components like armature, stator, etc were the same though.  Prefix is likely different?

Come on Sarge, do it right

Hoping to do it cheap and right. I think the armature is definitely the same. Will get those parts out of the shed tomorrow and post some pics for comparison. However, will work on my DT1E first. Had injector oil leaking from behind the autoluber pump wheel for some time and have the seal to hopefully fix it. Also noticed it appears over time the auto lube trickles (via gravity feed) into the carb. Want to ensure the steel ball is in the check valve, too. Maybe a clean up of the carb will square it away, as never had any real problems with the 250 in the past. BTW, good to hear from you, Dave!

Got the two yokes & armatures out today and did a comparison...interesting findings. GS114-02 12V  Yoke is for the AT1. GS114-01 12V is for the 1970 200 twin. Yoke sizes appear to be identical, with -1 just about 1/8 in. taller. There are differences on the mounting plate, but both yokes will fit into the AT1. There are no designations on the armatures, but like the yokes, both will fit smoothly onto the left crank and align with the woodruf key. Note thinner magnets and larger armature for the 200 twin and thicker magnets and smaller armature for the AT1. Now, here is a thought...I recall there were a few upgrades to the 12v electric start systems. I think there were two upgrades of the yoke ass'y. and corresponding armature, which were featured on later cycles. Though not directly interchangeable with the early AT1s, if one changed out both components they would work in the earlier cycles. Might be a few other minor changes as well like the cam as well. Maybe what we are looking at is the first  and then a second revision (-01 & -02). Thoughts...?

That's awesome news.  I think you're probably correct.  That's a later model so probably a revised version.