Seca Turbo Rear Shock Rebuild

So how many people are rebuilding these old things???? Haha. I'd like to experiment with the Seca Turbo shocks on my '82 Seca 650. I found some for $40 and except for the surface rust they were still fine. I was about to take them apart so I could replace the old oil inside but all you have to do is remove the air nozzle and the oil spills right out.
So my first question is what do I replace the oil with? I literally have no idea.
Do I even have to replace the oil in the first place?
How much oil should I put in? I kept the oil that I spilled out and it looks like it's somewhere between 4.5-5oz. Should I put that oil back in.
Should I still disassemble the whole shock for any reason?
Does anybody have an opinion on the Seca Turbo Air assist shocks?

Thanks

 

I guess this wasn't a popular subject. LOL. It's all good. For anybody wondering if the air assist Yamaha Turbo rear shocks are a good idea I can only say YES! I spent $26 on mine that I found on Ebay and other then some rust they work GREAT! All I did was replace the shock oil which is incredibly easy to do. I also cleaned them out first with a degreasing solution. I was able to ask around different forums for more advice but there wasn't much out there. So, I bought some Yamaha Shock/Fork oil and put in 4oz in each shock. That amount was based off another guy's guess. Sounded good to me. I pumped up the shock to about 20lbs psi. The minimum is 14lbs and the maximum is 57lbs I believe. I have them at the lightest damping. Went for a ride and I was in heaven. They work great. I'm also a fairly light guy 165-170lbs so I don't require much. Safe riding. Cheers!

 

Shock rebuilding isn’t much of a thing because I don’t believe many of the XJ shocks are rebuildable.

I’m sure it would be much appreciated if you could share any “how to” information or lessons learned or anything. Even if it’s turbo model specific. That’s how we build the body of knowledge and hopefully help the next person facing the same problem.

 

If you have a lathe, a TIG welder, and can fab parts it can be rebuilt. Not worth the time or effort though.

 

Some shocks are rebuildable - koni/ikon being one make. Personally the original Kyb type are not worth the bother.
I built some front struts for one of my rally cars once - quite simply the cost (and availability) of uprated units has gone through the roof. So I cut the units open, put the oil to one side and just stripped the springs and valves out, getting to know what did what ( you have slow and fast bump as well as slow rebound normally). In a rally car you don’t want the fast valve opening, so I binned those, and shimmed the others till they felt right. The way I used to work out what did what was to use water as the damping fluid, otherwise I would have been an expensive oil soaked mess. It worked well, but took me all day. Finished off making screw tops for them so I could strip them again if needed.
Actually that was quite lucky - as soon as I started driving hard over the bumps I knew it wasn’t landing right - when I stripped them later I found I had made a mistake and fitted the wrong washer in one of them.
All in all an interesting exercise, but I wouldn’t recommend it. It did make me wonder where all the gubbins were when I opened my first bike forks though, I’m amazed given how simplistic they are that they work at all...

 

Clarification: shock rebuilds for XJ owners are not common for stock XJ equipment, as @k-moe points out it may be possible but the juice isn’t worth the squeeze.

of course shock rebuilds are generally common, just not stock XJ shocks.

 

70s and 80s Japanese bikes all of a muchness in this respect - barely adequate. Strange really, since they are the basis of the whole handling package. I suppose it was down to cost, and cost there is too if you look to buy modern gas pressured adjustable twin-shocks. Some manufacturers were clever and covered the stems with plastic shields to protect them, which helped, especially if they were adjustable as well. Hagon did some for the xj.
Mostly though rebuilding is not worth the bother...

 

Everyone weighed less back then. Not as much shock-absorber (dampner) required.

 

What exactly am I leaving out?

 

Don't know - maybe nothing.