Next is the rod. On first view, no pitting, but obviously driving the bike in the rain, water collects on top of the sealing and starts the rod to rust. Bad thing is, the rust ist directly in the driveway of the sealing. I bought a piece of stainless steel, to machine a replacement shaft. First I welded a mount for my Lathe, to center the old shaft. After I cut it an machined a center on the shortened end, to fit to the replacement shaft. Goal was to keep the mounting, and hard-solder it on the replacement shaft. Special 730°C hard-solder material with high strength. Finally after soldering, the assembly was machined to origin diameter and polished. This should be solid. Cutting the origin shaft with a hand saw I noticed, it´s a very soft steel grade.
The thread is a very unusual size, M7x0.75 mm
At least the new shaft never will rust again.
If there is interest, I can continue posting my further steps

Very nice work Wessi!

I am so envious of you guys that have your own lathe, mill, etc. or access to a machine shop!

You're effort to salvage and improve these shocks is very commendable!

Fantastic Wessi, I'm envious of your work.

Top stuff - you could offer a rebuild service for us on this side of the Atlantic!

Speechless--& so was my lathe. Asked it if it could do 'that' & it said nothing. Love your work. Apart from that--my MX250 had those shocks New in "73 & looked the part but don't think they were as trick as they looked just good for extra oil & cooling--well suppose that 'was' pretty trick back then. I think the YZA version had changeable jets for damping inside a blanked off couple of screw holes but i might be dreaming. Interesting too how most pics you see shows those shocks mounted back to front--should have the reservoir to the front.

Continue with the cylinder. Inside is completely rusty. No chance to re-use this part. I purchased a stainless steel tube, outside 25mm, inside 21mm. The final inside has to be a smooth surface, therefore I bought a used reamer, 22 H7 and bored the inside of the tube. This inside diameter, stock top- and bottom valve fits perfectly tight. As the cylinder assembly is hold inside the stock by top and bottom valve, outside diameter does not matter, 25mm is ok. Beside this, tube is stiff enough, better than stock

Biggest hurdle for my shocks was the bottom valve ( left one on first picture) was completely rusted. After sand blasting I saw, it´s totally scrap. No chance to reconstruct it. Luckily I got a better one from a friend, so I could start to put everything together. The rubber damper on top of the rod have been worn and lose, so I bought on Ebay 2 rubber plugs for lab flasks in the right diameter. Bored the center hole and cut it to length. Now I am waiting for the spring, coming from chrome shop. I told the shop owner, not to polish the spring after de-chroming to achieve the original rougher surface. Have to pay 50€ for both springs to re-chrome. Very fair price, I think.
To be continued

Meanwhile I put everything together. I have to mention, that I didn´t thrust the hard soldering and welded the shafts with stainless steel and a MIG welder. The cup under the upper mounting eye is completely filled with welding, after, I equalized it on my lath (shown on 1st picture)

I know, better would have been a bigger radius in the edge...
Anyway, here some thoughts, why I did the repair this way:
-The origin shafts are soft steel and chrome plated. Fine, but mostly rusty. Attached a picture of 4 shafts, hardly corroded specially underneath the sealing, where water collects and never will evaporate. So staining is most likely, even when the shocks you buy are fine at first view.

My stainless steel rods are harder and more water resistant. The hardness of my bushing, made of bronce, is lower and lubricated by micro-amounts of oil, passing by the sealing, as it is usual in machinery. So in worst case, wear will happen at the bushing.

The complete origin shocks seem not to be build for long life time, maybe to save costs
My bronze bushing is more suitable to guide the rod, the origin guide is very soft aluminum/zinc alloy, same counts for the piston. I have 4 shocks, only one of them has a piston ring. Cylinders of the shocks are all the same, so wear at the 3-ones without ring is predictable. Have a look at the oval piston, shown some posts before. Most likely they didn´t mount the rings after some years anymore for cost reasons, the 3 pistons don´t have a notch to allow carrying a ring.
My cylinder is drilled with a 22h8 drill, which creates sufficient "honing" surface to keep oil on the walls and has an even an smooth surface, to protect the piston.
To be continued