JetsRus carries some sizes of replacement jets, but not always in the exact required sizes.
http://www.jetsrus.com/a_jet_kit_street/kawasaki_550_KZ550_1980-1983.htm
They are likely close enough to use, though, with the exception of the #86 main found on the 82/83 kz550H Gpz. For those, replacements might need to be found in another brand such as Keihin or Dynojet.
For details on the Tk26 style main jets, including different brand replacements, please refer to the Tk22 website.
TK22jetsAndDrills.html
The Tk22 carbs use the same syle of main jet as the Tk26. That page also has details on drilling jets in case none are available in the correct size.
The Tk26 pilot jets, however, are not the same as the Tk22 pilots. They do share the same threads, but differ in length etc.
The Tk26 pilot jets do look very similar to a type of pilot jet used on Yamaha motorcycles, but are not swappable. The Yamaha pilot jets do not have bleed holes so they will not function properly. Here is a comparison of the two types of jets.
The Tk26 main bleed pipe looks very similar to the Tk22 bleed pipe, but they are longer. Some dimensions, including the threads, are the same, but they are definitely not swappable. The needle jet, which is part of the main circuit, (silver jet in the photo below) is also not swappable with that of the Tk22.
The main bleed pipe of the Tk27 and later Tk26 carbs are similar to the early Tk26 main bleed pipes, but they do not use o-rings to seal the pipe. It appears to use a taper chamfer to seal the pipe to the carb body. The needle jets are also different on the later Tk26 carbs. The needle jets on the Tk27 carbs are different from both Tk26 variants.
The intermediate jet and intermediate bleed pipe are only found on the 82/83 Gpz550 version of the Tk26 carbs.
