So I promised a rear shock re-build thread.
But I had to wait until the 10x19x7 seals came.. Unfortunately I bought them from China because I couldn't source them locally, and no one in the UK seemed to sell them on e-Bay. So I decided to wait. Not least also because they were considerably cheaper. £5.50 for 10, posted from China...
With the belp of these forum posts I also could see what I had to deal with:
https://www.mzriders.com/viewtopic.php? ... cks#p32728
https://www.mzriders.com/viewtopic.php?f=20&t=7360
Warning- The images are large. If you don't have a widescreen or large monitor you may need to Right click on the image and open as a new tab to see the whole image without the forum frames cutting the images..
Thank you
https://www.ebay.co.uk/itm/ID-10mm-TC-R ... 2749.l2649
I must say, I had four old shocks that 1 of each pair had unfortunately blown and leaked oil everywhere.. So I decided to take them apart and see exactly what is needed to re-build, if possible. Out of the four I had, one of them could not be disasembled (the top eyelet could not be unthreaded from the main rod- but instead it was riveted in somehow).
If you have a threaded top eyelet.. then you have the technology- you can rebuild it!
So. I'm documenting the 4th one.. after having a practice on the other two..
So you start with your shock as shown:
And first you'll want to remove the top retainer pieces. To do this, you will need to compress on the spring, potentially quite a lot in order to fetch out the two individual retainers..
Then you can pull off the spring upwards, and with it the plastic cover.
If you have a threaded eyelet, you can unscrew the locking nut and eyelet.
And you will now encounter the threaded retainer of the rod and assembly.. It's not too much of an issue, thre are special tools that MZ say to use- but I used a small punch. Once it starts turning, you can use circlips and easily unscrew it. You may have to clean out the notches quite thoroughly from dirt.
Once that is removed, you will very likely have to re-install the eyelet, because although the retainer is free, you will likely find it very difficult to remove the shaft and the internals. You merely need to pull on these, but I myself had to use sacrificial socket extension and a hammer..
And there the inner assembly comes out of the lower shock.
And if you pull on the eye more, you can detach the assembly from the tube that encompasses it.
Now you can take off the eyelet and remove each component, I didn't have the lower seals, so I merely took the top most oil seal unit off.
You must now inspect the shaft. I found that all four of mine were in very poor condition from either previous owners dismantling the system, or it seems rub or neglect wear.
This one isn't too bad. There are no gauges, just wear witness marks. That said- This particular shock was not leaking before I took it apart.
Now to drain the old oil.. And this is what mine looked like:
You'll want to be careful at this stage, as this 'star' looking thing sits at the bottom of the tube and will likely fall out.. make sure you don't forget it..!
So, this device holds the main oil seal.. It is two parts
And can simply be prised apart without too much effort as so:
After splitting the two pieces and prising out the old seal, Make sure to clean the area
Dig out the old seal, and push in the new one.. Not a lot of effort is required here. You might want to lube a bit with ATF.
And now.. It's time for re-assembly already! Obviously clean everything. Now, you may have noticed that I have not loosened up and removed the adjustment sleeves. The fact of the matter is, I tried to remove one but the only way to do that was with hammering. They are stuck solid and unless you have a replacement to use, I wouldn't bother. You will destroy the shock adjuster, and if you do get it off, you'll have to do a lot of cleaning and cleanance gapping in order for it to go back on smoothly. I myself have never felt the need to adjust, and even if I could I would only use the facility one a very blue moon. I rarely have passengers.
This is the main rod assembly and order of items for installing it into the inner tube..
But first.. Time to put that star shaped thing into the lower shock assembly, and the inner tube!
It took me a bit of time to find out what oil capacity is required. The MZ official manual and the MZ Haynes manual say nothing at all about capacity- they just say "fill with oil", which isn't necessarily helpful. If you measured how much came out and presumed it hadn't leaked before.. then you might be re-filling with incorrect capacity.
But, I found this website, and the capacity seemed about right at 80cc...
http://www.sweller.co.uk/mz/workshop/wrk_shock.html
I myself used ATF.
And once the oil is installed and the tube and star, push the assembly in the inner tube... and then lock in place with the assembly retainer..
I used circlips once again to tighten up the retainer as much as I could by hand. From there, I used a punch and a hammer to tighten the lock by another quarter of a turn.
And then the rubber bung (I suppose this is a bump stop)..
I neglected to previously mention, but this item fits inside the black plastic upper rod gaurd...
You will then likely want to install the eyelet and retaining lock nut.
Then re-install the spring, and the plastic inner guard and then you can pull on the eyelet and push down on the spring to install the two piece retainers..
The lower bushings are easiest to assembly by putting the rubber part in half way, then insert the inner metal bushing. then you can align them from there.
And now you have a re-built shock..
And a very dirty washing jug...
They may leak again..... I don't know, my rods weren't in the best condition for me... But with new oil seals and a clean of the assemblies and new oil may be all that is required..
It's worth a go for the price of a single seal (or 10 for £5.50), and 80cc of ATF!!
