How to Service Your stuckdown ATA cartridge

PB Forum :: Mechanics' Lounge
How to Service Your stuckdown ATA cartridge
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flag Nick-M2r
Posted: Feb 12, 2010 at 6:19 Quote
Had this on MTBR for awhile and have seen many threads on here about people having problems with leaky ATA carts, this guide will show you how to fix it.

Hi all

Well here is my little how to that shows you how to teardown a ATA cartridge and give it a bit of TLC. If your ATA Cartridge is stuckdown, this guide will show you how to remedy the problem. MODS, sticky this if you wish

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WARNING: Im not responsible for any damage you cause to your fork, persona or surrounds. This repair is simple if you have some mechanical inclination and common sense. Care must be taken as these Carts can contain air at VERY high PSI's, undo something the wrong way and you'll have yourself a pretty dangerous speargun.

Righto now the legal Bull$hit is outta the way, onto business!
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First what is a stuckdown ATA cart?
Your cartridge is stuckdown if it does not return to full extension despite:
1- Winding the ATA knob to max extension
2- Pumping ridiculous amounts of air in the ATA chamber

Also, another potential give away is if your ATA chamber appears to be losing pressure and the fork keeps creeping down in its travel.

Well first off, here is the likely cause of your stuckdown problem (shown with my awesome paint skills )

photo


Now I performed this fix on a 888 ATA WC, but I dont see any reason why it wouldnt work for 08/09 55/66/888 ATA forks, and also for 07 66 forks, the only difference would be the cart size.

Only tools needed for this job is a 12mm socket (for the 88Cool , shifter, o-ring pick, and fork oil, also handy to have some drip pans and rags...

Right, time to get back full travel

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STEP 1:

First, deflate all the air from both the ATA chamber and PAR assembly, remove your fork from your bike and pull out the ATA adjuster knob (dont forget to set it to max), if you dont know how to do this i suggest you put the tools down now, also, in the case of the 888, its best to remove you crowns aswell.

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STEP 2:

Next lay the fork down flat, then using a 12mm socket (in the case of the 88Cool , undo the ATA footnut. Now when the nut disengages the threads there will probably be a loud clank and the cart will fire up into the lowers, dont panic, this is normal on a stuckdown fork. Some oil will also probably spill out, be sure to wipe it up, then pour the remaining oil into a drip pan.

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STEP 3:

Next, using a cassette lockring tool, undo the ATA top cap and lift out the entire ATA cart

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STEP 4:

Have a friend firmly but gently grip the cartridge body with an old tube, then using a spanner or shifter, SLOWLY (and I do mean SLOWLY) start to undo the ATA cart. THIS BIT IS CRITICAL, IF YOU DONT DO THIS BIT CORRECTLY, YOU'LL HAVE A CARTRIDGE BODY/SHAFT FLYING ACROSS THE ROOM. Undo the cartridge VERY SLOWLY until you start to hear air seeping out, when you hear this, STOP UNDOING THE CART. This is where all that air you were mysteriously losing has gone, and when you tryed to pump the cart back up, you added to it. Wait until the air stops coming out, then undo and remove the cart. If you hear air being sucked into the cart when you are pulling it from the body, this is a dead give away that your o-ring was undersized, it is bleeding into the vacuum within the cart. When you pull the piston out, you may suck up the PAR assembly, this is normal.

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STEP 5:

You have now taken apart the ATA Cartridge, lay all the parts on the table and give them a good wipe. Should you wish to perform Renegades PAR removal mod, now would be the time.

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STEP 6:

Now the undersized (or frayed/damaged) o-ring that is causing your problems is the one on the right. To fix this, go down to a local o-ring supplier and get a few o-rings that are slightly larger. You may also wish to replace the other visible o-rings, take them aswell and have them sized, its also best if you buy a couple of each, always good to have spares!

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STEP 7:

Once you have replaced your o-rings, drop the PAR assembly back into the cart (dont worry if it dosent fully seat at the bottom, it will when you pump it back up. I like to pour about a cap full of 5wt oil into the cart to keep everything slippery smooth, also lube up the piston and o-rings, make sure the top half of the cartridge is fully extended (bottomed on the rubber bumper), then reinsert it back into the cart. Use your spanner and tube and tighten her up, dont get heavy handed on the torque, the threads are made of Aluminium.

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STEP 8:

Congrats, you have service your ATA cart. Now reinstall it back into the fork and check the marz website for your forks oil volume in the ATA leg, fill the oil and pump her back up, and if you have done everything correct, welcome back to full travel!

Now make sure you dont go hucking the 40 foot gaps just yet, take the first few rides easy to make sure that all the internals are properly lubed and bedded in.

I performed this fix on my mates 888 ATA WC about 5 months ago, and it has worked flawlessly ever since (5 months of DH/FR) so the fix works.

SUCCESS = BEER
flag wafrojo
Posted: Mar 1, 2010 at 11:09 Quote
sweet read will defo be looking into this on mine. any idea on what size o-ring it would be on a 09 55 ata?
flag dannythekiwi
Posted: Mar 1, 2010 at 11:25 Quote
These threads are fricken awesome! Props for breaking it down to laymans terms.
I don't have a Marzocchi fork, but I respect the effort put into these threads!
flag admarshall
O+
Posted: Mar 1, 2010 at 11:32 Quote
Good effort man - my 55's ata2 isn't stuck (yet). It's nice to know how it all works without breaking it apart yourself and potentially damaging it.
flag wafrojo
Posted: Mar 1, 2010 at 12:41 Quote
yer agreed with the guys above. always been scared to take em apart incase something jumps out and runs away like. but all looks pretty simple and managable
flag SSBone
Posted: Mar 18, 2010 at 13:14 Quote
what if my ata knob just won't move... it's stuck at 180 mm and i can't turn it...
flag wafrojo
Posted: Jun 20, 2010 at 2:36 Quote
not recommending this to anyone but I'll tell what I did cause I was skint at the time.
take the forks of and pull them upwards to perhaps squeeze the air out from where's it leaked to into the main chamber,
then push the air valve to let the air out and repeat, keep doing it till you can pull it up to full travel with ease and compress them with ease and you are sure there's no more air where it's leaked to. then pump them up to your psi and they should be working.
like I said it's worked for me but perhaps it won't work with you.
flag mtblocos1
Posted: Mar 30, 2011 at 11:02 Quote
GOD BLESS YOU for posting this!

Beer
flag ridinsaila
Posted: Jul 1, 2011 at 23:52 Quote
hey,
i started to do this fix to my ata cartridge and tried to upgrade the seals to a slightly larger ones. but they didn't fit. and then to make matters worse i lost two of the seals (the two inner seals). i was wondering what the size of all seals in the cartridge itself as i don't have them any more to get resized. thanks for the great post
flag radatabs
FL
Posted: Mar 11, 2012 at 1:56 Quote
i know its a stupid question but on the other leg where would I put the air travel adjust spacers to lower the fork?
flag charliefandango
Posted: Jan 23, 2013 at 13:46 Quote
I recently had my 2009 Marzocchi 888 ATA WC diagnosed with a blown cartridge. The shop's tech says because the fork is no longer produced by Marzocchi that a replacement part or rebuild is impossible.

What happened was I hung my bike up on wall hook in my garage and noticed the next day that oil had leaked out of the top of the right fork. Oddly this happened sometime after I took my bike to my local bike shop to get the oil replaced as I had not done any real servicing to the fork since I bought in 2010.

So would your ATA rebuild fix the problem? I do not know very much about the internal workings of my fork's cartridge and I am wondering if its a blown ATA or the TST is blown, or both?

-CF-
flag wafrojo
Posted: Jan 24, 2013 at 14:02 Quote
Depends, if its a cracked cart then itll need replacing which you said would be impossible, or the o rings may be shot therefore that'll be easy to replace. Although if it's coming out the actual lock out cap (right leg?) and not from around the nut - it's shot and new cart. Basically a new cartridge is out the question, best is to try and source a second hand fork of the same age and swap the cartridge over.
flag wafrojo
Posted: Jan 24, 2013 at 14:05 Quote
Correction* not the lock out cap, ata nob
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