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Marzocchi Air shock ( TST & WC ) bleed or rebuild.

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Marzocchi Air shock ( TST & WC ) bleed or rebuild.

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Posted: Feb 13, 2010 at 19:24 Quote
I have recently purchased a roco TST air shock to swap out for my coil. Little did i know oil had gotten in the wrong spots and it was not making nice sounds. Sending the shock into marzo would be time lengthy and costly, So I deceided to open it up and do the work myself.

This Guide is for people wanted a good bleed on there shock, or who need to replace their seals because its all accesible and fairly simple. I began with minimal tools, one of which I had baughten and never used untill this day to remove the nickel coated air can. Along with a philips head, a flat head, adjustable wrench, allen keys everything up to a 5mm, and shock oil.

Methods I used are probably not the right ones, but being as how the shock is so simple they worked.

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trusty tools.

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Vice. Before you try to work on your shock, your going to have a VERY hard time without a vice. its possible but very difficult, and I wouldn't recomend working on your shock without one.

1. Decompression the main cylinder and then the boost chamber so both have no air in them.
2. Unscrew the boost valve cap with an adjustable wrench and set it aside. You will see a small silver piece of metal sitting in there, leave it for now.
3. Unscrew the black piston, yes it simply unscrews and pull it away and out of the main air chamber. At this point there will be lots of oil everywhere, so be prepared to deal with it. To keep oil contained, have the shock in a vice like such.
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for anyone that has worked on a coil shock, its the exact same pretty much but reversed.
4. ( Skipping steps..) Remove main air cylinder, and the piggy back and remember to check the seals and see if they need to be replaced. At this point, you should be looking at your shock dissembled.

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(air can is still on, but needs to be removed) Top right is the TST damper, along with screws and seals. Top left is the " black piston". Below that is the rebound rod, and below that the piggy back assembly.

Once everything is dissembled, and all the seals are checked and the bad ones replaced, we can begin putting it back together. Personally, I had to do this 2 or 3 times because I forgot to put in some seals. Make sure everything is there and nothing is missing before you start the rebuild...

1. Judging that you are doing a rebuild, and stripped the shock down as I did we start with installing the rebound piston to the main body, and then the seal for the air can.
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If yours is looking like this so far your good.. I am aware of the damage on the rebound piston, no seal goes over it so its fine.

2. Remove the main body of the shock and place it aside.

3. put the black piston in the vice, and fill it up with oil untill the level of oil is around the middle of the threads.
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4. Take the main shock assembly, and screw it back onto black piston. do this slowly or you will loose oil, causing air in the system and you will have to do it again.
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Then flip the shock around.
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5. Install the TST piggy back onto the shock assembly. If you compress the shock before you put this on, the oil will leak out and you will have to fill it up again.
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At this point, you should be almost ready to bleed the shock. Now if you cant afford / dont have time time to buy a syringe to bleed it properly, you can cycle it untill air leaves the system. It wont be perfect but it will be ALOT better then before. - edit i am surprised how well this method work. I only removed the bleed port screw to complety drain the oil, then i put it back before i filled it up again. Shock works really smooth and queit too, good method, prob just as good as using syringe.
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While the shock is extended, the fluid will go down. When its compression, it will come up. If you have cycled the shock and there seems to be low oil in the piggy back, fill it up to the threads and keep going. ( only fill while shocks compressed.)

<Photo does not exist: 4590901> oil level around where I want it, now time to start closing up the shock.

6. With your shock pounted in its current position, extend the main piston so the oil level in the piggy goes down a little bit. Put in the LPI or lfi ( round silver metal thing) without the screw, so you can make sure you seal it with no air in the system.

<Photo does not exist: 4590891> Its okay to have oil ontop of the cap, but get rid of as much as you can.

7. When you set the height of the LPI ( round silver metal thing ) you can begin the final steps of the reasembly. Slide the air can down onto the assembly, and screw it into place.
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The black piston will be hard to extend, but thats okay leave it how it is. The air can makes a negative air chamber with the piston when you put it on, so it will want to keep the black piston in as far as possible. It will stay that way untill you pump air into the shock...
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Where I finish... <Photo does not exist: 4590878>
I don't Have a shock pump, I kind of forgot that when i depressurized the shock. Getting one tomorrow and will post if it works.


I find this shock more simple to work on then a 888 rc2x, because there is a rod to adjust the rebound, the rod which does the rebound damping, a seal which holds air both positive and negative, and ya. Its a very simple shock to work on. Learning how to keep it running smooth will only elongate the life of your investment.

Yes I do understand that my warrenty if void and you will have to as well. Also the methods used in this guide are brutal compared to the right ones ( due to lack of tools ) but get the job done as most the work is done by hand. The next post I will post will be mods to the TST dampner, got a bunch of shims from an older shock so when I get the shock pump I will keep posted...

If any of the pictures are unclear, you can most likely find one of the same in my album/

Just though I would give you guys an idea of whats going on inside the Roco if you did not already know.
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Posted: Feb 14, 2010 at 13:06 Quote
I know have a shock that runs better then my coil.
I am really impressed by the air can, i was pretty super sticious becuase there is 0 compression dampning, but that makes the ride that much better..

I was going to modify the shim stack in the TST catrdige, but theres no point. full open feels perfect, and full closed = no pedal bob whats so ever. things inbetween are a little iffy, but i normally run it full open.
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Posted: Feb 17, 2010 at 19:40 Quote
worksSmile <Photo does not exist: 4609508>
flag kguite
Posted: Aug 6, 2013 at 10:50 Quote
Thanks for this, I watched; https://www.youtube.com/watch?v=c9PkXo9WcIw
but its unclear for some parts, this bleed info was useful!
flag machuqueiro
Posted: May 8, 2016 at 15:21 Quote
after my last rebuild
during the bleeding the tst works
but then on the bike with the rigth pressure the tst does not chang compression
anny ideas ?
flag ermalkoci
Posted: Dec 26, 2017 at 5:44 Quote
machuqueiro wrote:
after my last rebuild
during the bleeding the tst works
but then on the bike with the rigth pressure the tst does not chang compression
anny ideas ?

With a high level of assumption, I would guess too much oil.
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