Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
No as they are cast in but somewhere on the site is an address for a man in Huddersfield who will machine out the old one and shrink a new piece of cast in and machine that to size.
Anyone with a medium sized lathe could machine the old retainer out. Re lining a drum is not too much harder, I did mine a fair few years ago, hardest bit was smuggling the new cast iron liner into and out of the freezer without a telling off from my Mrs, second hardest job was heating a hub up with bearings still in without damaging them as I couldn't get that retainer to move, even with a 1" bar welded to the retainer and the sprocket clamped in a leg vise allowing me to use sledgehammers. Worth it though, as has been said these hubs can be hard to get. The kind of job that let's a lathe pay for itself in short order. You could easily cut the retainer out with a drill or even a dremel and patience.
As you have nothing to lose and if not in a hurry. If you want to get them to send your old hub directly to me I will try to sort it out one way or another. Let me know and I will PM my address. Obviously I can make no promises but will keep you informed.
According to CSMNL these have the same hub.fits modelsCB500 JAPAN CB500K0 FOUR 1971 USA CB500K0 FOUR AUSTRALIA CB500K0 FOUR ENGLAND CB500K0 FOUR EUROPEAN DIRECT SALES CB500K0 FOUR FRANCE CB500K0 FOUR GENERAL EXPORT CB500K0 FOUR GERMANY CB500K0 FOUR NETHERLANDS CB500K1 FOUR 1972 USA CB500K1 FOUR ENGLAND CB500K1 FOUR EUROPEAN DIRECT SALES CB500K1 FOUR FRANCE CB500K1 FOUR GENERAL EXPORT CB500K1 FOUR GERMANY CB500K1 JAPAN CB500K2 FOUR 1973 USA CB500K2 GENERAL EXPORT CB500P JAPAN CB550 FOUR 1975 CB550K0 USA CB550 K1 FOUR 1975 USA CB550 K2 FOUR 1976 USA CB550F SUPER SPORT 550 FOUR 1975 CB550FK0 USA CB550F SUPER SPORT 550 FOUR 1976 USA CB550F1 SUPER SPORT 550 FOUR 1976 AUSTRALIA CB550F1 SUPER SPORT 550 FOUR 1976 CANADA CB550F1 SUPER SPORT 550 FOUR 1976 ENGLAND CB550F1 SUPER SPORT 550 FOUR 1976 EUROPEAN DIRECT SALES CB550F1 SUPER SPORT 550 FOUR 1976 FRANCE CB550F1 SUPER SPORT 550 FOUR 1976 GENERAL EXPORT KPH CB550F1 SUPER SPORT 550 FOUR 1976 GENERAL EXPORT MPH CB550F1 SUPER SPORT 550 FOUR 1976 GERMANY CB550F2 SUPER SPORT 550 FOUR 1977 EUROPEAN DIRECT SALES CB550F2 SUPER SPORT 550 FOUR 1977 FRANCE CB550F2 SUPER SPORT 550 FOUR 1977 GERMANY
Just shows how much you can trust the lists from CSMNL then.