I just replaced the ones on my '88 K75S with Wilbers springs. Wilbers is what is readily available in Europe just as Progressives are on your side of the big water. If you are unlucky like I was, a previous owner will have used heavy and inadequate tools in a hamfisted way, leaving burrs and scratches on top of the tubes. I had to use a Dremel to smooth them out.
I put in a longer bolt - metric - so I could compress the caps enough to gently pry out the locking ring. And I used a 22mm wrench to keep the end caps from turning. I shall probably never use that size wrench again. Then I used the long bolt to lever out the end caps that were now protruding about 8 mm. There is an O-ring holding it in place. It's not threaded.
I really had to wrestle them out because of the burrs left from a previous owner. And I cursed more than even Chris Harris does in this YouTube video where he disassembles a R65 fork. Looks very much like mine did.
This tutorial from the German flyingbrick.de site was a great inspiration. It's in German, but the pictures a very instructive.
http://technik.flyingbrick.de/images/a/a1/31_gabeloel.pdfWas it worth it? Absolutely. Last season I replaced the rear shock. Great improvement over the probably original shock. And the front springs were the original type with two separate springs and two spacers in each leg. Bike currently has 144000 KM on it.
