Swing arm comparisons.
With axles, adjusters, and pivot bolts.
XS650 12.5 lbs
TX750 13.8 lbs.
YZ125 11.8 lbs.
A fair amount of the weight savings come from hollow axle and pivot bolt on the YZ set up about .7 lbs. The YZ pivot bolt and axle are shorter and would not work on a stock frame or swing arm.
The XS and TX750 arm are near identical dimension wise, the TX750 is about 1/2" longer axle to pivot, the shock mount outer flange is a bit wider than the XS650s maybe an 1/8" but the inner mount and all other dimensions are the same.
The YZ arm is about 1/16" wider at the pivot. and the pivot to axle length is 4 1/4" longer. The YZ pivot has beautiful dual needle bearings (4 bearings), needle thrust pivot bearings, and full dirt seals.
The pivot bolt and axles are the same diameter on the 650 and 750 arms. The YZ125 is a little narrower at the axle but there is plenty of room for the brake, sprocket, and tire.
The axle on THIS YZ arm is 20mm the same as the XS. The pivot shaft is shorter and a bigger diameter than the XS shaft so that would mean work to use it on an XS650 frame.