@YzDt85 If you mean the DT200R 3ET alloy swingarm, as far as I know it's the same overall length and uses the same pivot/linkage bearings as the DT125R steel arm (and takes the same All Balls 28-1212 pivot bearing kit). Here are some pics of a bench mock-up I did a couple of years ago using DT125R crankcases and rear hub mated to 3ET alloy swingarm, rear wheel spacers and caliper hanger. As you can see the 428 sprockets lined up quite well (I also had to use a 3mm thick M20 washer between the caliper hanger and swingarm to get it as good as it could possibly be with the items I had to hand).
IMO the engine boss at the rear of the crankcases dictates sprocket alignment probably more than the frame, and I reasoned if the sprockets aligned with the original hub the wheels are probably in alignment as well (although having no roadworthy DT125R at the time meant I had no way to check this).
[image: 52556684503_16239c8d2f_b.jpg]
[image: 52556439059_a5cefa37d8_b.jpg]
[image: 52555691007_9305583e9f_b.jpg]
Don't forget the all-important swingarm side clearance, it's a lot easier than Yamaha makes it look and if you get this right you can get the arm to fall under it's own weight with <1mm side-to-side play which massively improves suspension compliance and chain/sprocket wear:
[image: 52540603964_8d06666c50_b.jpg]
[image: 52540604869_4557759cdb_b.jpg]
[image: 52540604294_15fa260c81_b.jpg]
Top DT200R tip; the plastic mud flap that protects the rear shock wears the (basically priceless) alloy swingarm away at the rear of the linkage bearing over time so it can be helpful to install something to prevent this. A lot of people with modern Huskies, KTMs etc. JB Weld a coin to the surface of the arm as they're prone to it as well.
I considered all that mud and chain lube floating about to be quite a harsh environment in which to try and glue two pieces of metal together so on my 250EXC I used the plastic sleeve which you get inside one of those boxes of sticky labels they sell in the Post Office cut open and cable tied on.
[image: 53693206276_85d64b2e93_b.jpg]
