Not sure if this has been discussed (I'm sure it has), but I have 2 bikes that need new fork tubes. My '69 DT1 and my '70 CT1. I'm getting ready to start rebuilding these and I'm not sure what to do with the fork tubes. I'll try to attach pictures of both. Is there someone that refurbishes these? Or is there someone that sells new replacements? They are so rusted, I'm not sure they are salvageable. I'd appreciate any advise/direction.   

Franks fork tubes and DC plactic has the Dachi replacement fork tubes at a decent price. 

When I began working on my rusty, non-running 1971 CT-1 a year ago, the fork tubes looked close to your first pic. I avoided compressing the forks and dug into the tubes by hand with paint-stripping discs cut up, and lubricated with WD40. After the big rust came off, I went to wet/dry sandpaper, ending with super fine, still using WD40 to lube it. I was surprised that they came out very smooth, but pitted. I've never disassembled these forks, and have put 1600 miles on it since. The forks work perfectly, with the original oil. I never intended to do a full restore, just to get everything working well, and spruced up.



  

I don't think you will be as lucky as Tom was with his bike. From your photos it looks like all the chrome has rusted off, so rechroming or replacement I think are your options.

If you go with the Dachi/Daichi tubes do a search here for comments and tips, as I believe some 'fiddling' may be needed to get things to fit back together. When I was doing a '68 DT1 I was fortunate enough to come across some very good NOS tubes (I really think they were actually "take-offs"), the Dachis were not available at that time.

I am in the same boat as you with a '70 AT1, and have not been able to source replacements (of any kind other than used). As I do not see Dachi/Daichi tubes for that model, I found these guys online. I intend to go there next when I get to that stage in the project.

www.ecgrinding.com/motorcycle-fork-repair.html

If you can get replacement tubes, that will probably be the cheapest option.

If you cannot, or want a lasting job, take them to a hydraulics specialist. They will probably be able to get them ground down and built up with hard chrome like they do with hydraulic cylinders.

Factory fork leg chrome is usually just a quick flash of show chrome and grind to size, more for aesthetic reasons than durability. Chrome is porous and the thin coat, (probably a couple of microns thick) allows water to get to the underlying steel, which then rusts and blows off the chrome.

Hydraulic cylinders are finished in hard chrome, which is a much more durable bearing surface than show chrome, and up to 0.5 mm or more thick chrome plate.
You will not have further pitting problems.
All my pitted fork tubes get hard chromed. It is quite expensive though, probably the same as buying brand new genuine tubes.