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Discussion Starter · #1 · (Edited)
The following procedure is a remedy for ATA auto wind-down for the Marzocchi 66SL ATA fork. It may apply to other ATA forks, but since I have not performed this fix on any fork other that the 66, I will not make that claim. This procedure was the result of my own attempts to understand, and correct the auto wind-down that started happening after owning the fork for 8 months. After speaking with Marzocchi techs about this issue, I was informed that they had at least 4 approaches to correcting this issue, but after hearing that, and feedback from other fork owners that these "fixes" were not necessarily working, I decided to find out on my own why this issue was happening. In all cases, there appears to be a lack of friction in the ATA adjustment system. Simply put, the knob you turn on the top of your fork turns a shaft, and that shaft has four depressions in it. The top cap of the fork has two detents, each comprised of a set screw, spring, and ball bearing; these two ball bearings are pressed into the shaft depressions, providing a detent position for the adjuster. Each click you hear when you turn the knob on top of the fork is the sound of the detent balls being pressed into the ATA shaft depressions.
Marzocchi has tried making a new ATA shaft, with deeper depressions, has tried a thicker o-ring [the one that is supposed to keep oil from collecting in the top cap] to add more friction, and has tried a different spring [unfortunately, one that was too short], but no one method took care of the problem 100%, to my knowledge. My approach was to replace the stock detent springs with ones identical in length and diameter, but of a heavier gauge wire, producing a much stiffer spring.

The stock spring from Marzocchi is identical to this one:
Type: Music Wire Compression Stock Springs Outside Diameter: 0.120 In. Wire Size: 0.016 In. Free Length: 0.250 In., 1/4 Spring Rate: 18.87 Maximum Work Load: 1.85 Solid Height: 0.119

The spring I have been putting into the ATA system is this one:
Type: Music Wire Compression Stock Springs Outside Diameter: 0.120 In. Wire Size: 0.020 In. Free Length: 0.250 In., 1/4 Spring Rate: 48.42 Maximum Work Load: 3.40 Solid Height: 0.155

After changing out the stock springs and inserting the news ones, I have about 6 weeks of riding time in on the modified fork, including two full days of lift assisted DH riding. I carried a machinist scale with me to measure the length of exposed stanchion before, and after every descent. There has not been any wind-down; not one click, not one millimeter, the fix worked.

I have performed this same fix to three other 66SL ATA's. All of them have reported no auto wind-down since the fix.

I realize, from a statistical pint of view, that 6 weeks and four forks is not a proper test group size or period, so I am not making any grandiose claims. What I am saying is it does work, and that you now have an alternative to sending the fork back to Marzocchi; you can do this fix yourself, if you have any mechanical aptitude. The parts are cheap, and the operation should take you about an hour. I now do it in 30 minutes. Weigh that against not having your fork for three to six weeks, and maybe not getting the issue resolved.

The springs you need can be purchased from www.mscdirect.com. You can order online, the part number is 06810154, they come packaged 10 to a bag, and cost $5.53 for the bag. The instructions are as follows:

1] unscrew the top cap from the left leg using a cassette lock ring tool. It is totally unnecessary to remove air from either end of the cartridge.

2] compress the fork so as to raise the top cap and damper rod to a good working height. If necessary, release any air from the right leg [RC2] side to allow you to compress the fork.

3] stuff a small rag in the open fork leg, around the cartridge rod, to prevent any small parts from falling into the open leg.

4] using the appropriate sized allen wrench, back out the two set screws so that their exposed end in approximately flush with the threaded O.D. of the cap. Do not remove the set screws at this time.

5] looking down into the topcap, you will see a cir-clip at the junction of the schraeder valve and top cap. Using a small screwdriver, remove the circlip from it's retaining groove. If the clip drops into the cap, do not concern your self with trying to remove it immediately. You will have ample opportunity to do so after the cap is removed from the shaft. There is a washer underneath this cir-clip as well.

6] You are now going to remove the top cap. Turn your hand palm side up; place it underneath the top cap, with the damper rod between your middle and ring fingers. This is in case the detent balls drop out after the cap clears the shaft. Unscrew the cap, it's a left hand thread; your "catching" hand should follow the cap up as you unscrew it. Once the cap is clear of the shaft, and with your catching hand still underneath it, transport the cap to a clean bench or horizontal surface, preferably one that has a shop rag laid out on top of it, so as to prevent the detent balls from roll off of it. Carefully remove your catching hand, look to see if either of the balls fell into your hand. There is also a washer that is located inside the top cap; the underneath side. It may stick to the inside of the cap. Confirm the location of this washer; it is either stuck to the underside of the cap, or is still on the ATA shaft. If it's on the shaft, leave it there.

7] I f neither ball fell out, look inside the I.D. of the top cap. You should see a portion of the two balls poking out of the holes. Touch them with a small probing tool or a cotton swab, and see if they easily dislodge. If they do not we'll take care of it in the next step.

8] unscrew the two set screws the rest of the way and remove them. Poke a small probe through the hole, to push the detent balls through to the I.D. of the top cap. Now that the balls are out of the way, it's time to look at the springs. You may need to flush some alcohol through the threaded holes to remove and built up oil and grease. The condition of your springs may vary. They may easily fall out of the threaded hole, or they may need to be "unscrewed" or teased out of the hole. If you have previously tighten the detent screws in an effort to fix your auto wind-down, these springs may be damaged. Mine were that way, but the other three forks I worked on were not. The springs came out easily. Whatever method is used, you need to insure that you do not damage the threads in the hole.

9] The method I used to remove the damaged springs: I used a small cotton tipped applicator. This is not the typical cotton swab, it's smaller in diameter, and has a more pointed end. The typical cotton swab is too large to fit in the threaded hole. I lightly wet the cotton with alcohol, then inserted it into the hole, then rotated it in a "screwing a fastener in" direction. You are attempting to have the cotton applicator engage the spring, and thread it towards the inside of the cap, where it will exit the threaded hole, and fall out. This is the most tricky and delicate part of the operation. The second time I removed my stock springs, one of them had deformed so much that it didn't respond to this technique. I eventually had to use a microscope and dental pick, and carefully pried loose one end of the spring, so that I could catch it with tweezers, and remove it. Be careful not to damage the threads in the top cap.

10] Clean the balls and the set screws. Clean the threaded holes in the top cap; we want them as pristine as possible, because you will be using blue loctite in the holes later.

Re-assembly:

11] Get together these items: blue loctite, some grease [doesn't matter what type], some cotton swabs [bigger ones are fine], the balls, setscrews, new springs, and the allen wrench for the set screws. Stand up the topcap on your horizontal work surface. Dab a cotton swab in the grease, reach down inside the center through hole of the top cap, and dab some grease at the junction of the set screw holes and the center through hole. Again, dab some grease on the swab, and touch it to one of the detent balls. The ball should stick to the grease. Pick up the ball in this fashion, and again reach down into the center through hole of the cap, and place the ball inside of the threaded hole. The grease should keep the balls in place for the remaining operations.

12] Place the new springs into the holes from the outside threaded surface of the top cap.
Apply some blue loctite into the threaded hole, and screw in the set screw so that it is just below the surfaces of the thread on the outside of the top cap.

13.The washer that was inside the top cap, in the underneath area; if it is not still held in place in that position by grease and has been removed form the cap, go ahead and put that back onto the detent shaft. Carefully pick up the assembled top cap, put your other hand underneath it, and head over to the fork. Carefully slide it back onto the detent shaft, then thread it into place. It's a left handed thread, so you will be turning the cap counter clock-wise.

14] Now it's time to apply some tightening to the set screws. Turn each screw in two full turns, then a quarter turn at a time. Between quarter turns grab the cap in your hand and screw it up and down a turn or two to get a feel for the compressive force on the detent balls, You are looking for a solid detent feel, and some decent drag on the cap. Bear in mind that this feel will be different once you thread the top cap back into the leg. You can overdo it, so don't get greedy. Once you get to a point where you think it's good; using the cassette lock ring tool, thread the cap back into the fork leg. Pop the ATA adjuster cap onto the top cap/shaft, and turn it back and forth a few clicks, Again, you are looking for a solid detent feel, and some drag when you turn it, but it shouldn't be too difficult to turn. If it's not the right feel, unscrew the top cap from the leg, and adjust the two set screws accordingly.

15] If you released air from the RC2 side, reapply it, and go for a ride. I carried a small machinist scale with me to verify whether or not there was any remaining auto-winding. If you still have some wind-down, you will need to apply a little more load to the set screws.
 

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Good Job!

Fantastic work Renegade, thanks for taking the time to address this I am sure is going to come in handy for a lot of folks out there.
Did you ever research the negative volume adjust, I never have seen any corrections to the previous posts regarding this, which will be a bit misleading to others, and it looks like Vitox is MIA since I brought that to the forefront.
 

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Great info there. Especially the part numbers.

Did you try and remove the springs without taking the schreader valve out. With a dentist pic you may be able to remove the spring with the ball still inside and just replace the spring. Since the valve is still in there the balls cannot get lodged any where they shouldn't
 

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glad for the thorough post with part numbers and suppliers, Mine has still been issue free now with a whole season of DH riding but it is good to know there are things that can be done if issues arise.

I was also posting here to ask you if you got your ROCCO back from PUSH yet and what you think?

I just rode my PUSH DHX at Northstar riding some of the same trails and man I gotta say night and day difference. I was never unhappy before (excepte for fox's classic crapy rebound (always either too fast or too slow)) but now knowing what I was missing big improvement and the PUSHed ROCCO is supposed to be even better than the PUSHed DHX so hopefully you like it.

post on that too if you haven't already.
 

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Discussion Starter · #9 · (Edited)
Thanks guys. Sorry, no pictures; I tried to be as verbally descriptive as possible.

Glker, I have researched the negative volume thing, and I've concluded that it's a waste of time. The groove inside the cartridge does equalize the volumes with each stroke. I didn't edit my original post; I plan to do another write up of the PAR removal procedure that will exclude the negative volume setting, and include recommended pressures for post PAR riding.

Koffee, you disassembled your fork the hard way. :D Yes, you can simply take out the two set screws and try to fish out the springs from the outside, but they do pop out easier this way, plus it's a good idea to inspect the whole system. One of my detent balls was frozen in place by oily gunk, so I wouldn't have found that out unless I followed this procedure.

Warp, I can accurately measure +/- .010 inches with a starret scale, so no calipers needed.:D

Jesse, I actually might like my Pushed Rocco better than the Pushed dhx.I would want to put the dhx back on the bike and ride it for a while before I do a back to back comparison.
 

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Renegade said:
Glker, I have researched the negative volume thing, and I've concluded that it's a waste of time. The groove inside the cartridge does equalize the volumes with each stroke. I didn't edit my original post; I plan to do another write up of the PAR removal procedure that will exclude the negative volume setting, and include recommended pressures for post PAR riding.
What about filling up that groove with JB Weld or something???
You have good enough tooling at hand to hone the surface if needed, Rennie.

I mean, filling is easier than grinding, uh?

Sheesh... Would I have your tools and toys...

Renegade said:
Warp, I can accurately measure +/- .010 inches with a starret scale, so no calipers needed.:D
Showoff... :p :D
 

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Discussion Starter · #12 ·
Warp said:
What about filling up that groove with JB Weld or something???
You have good enough tooling at hand to hone the surface if needed, Rennie.
Warp, you wouldn't want to do that. The groove is a very important feature for the negative system as it exists in this model fork in stock condition. With each stroke of the fork, the negative and positive chambers equalize to an extent. Now I wouldn't mind having a second cartridge housing without that groove, just to experiment with......
 

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Renegade said:
Warp, you wouldn't want to do that. The groove is a very important feature for the negative system as it exists in this model fork in stock condition. With each stroke of the fork, the negative and positive chambers equalize to an extent. Now I wouldn't mind having a second cartridge housing without that groove, just to experiment with......
You can fill part of it to control the where the equalization happens... It could be just a small groove to allow for equalization at full travel, like it happens on a Fox shock.

I'd like to have one at hand and see for myself. I'm just giving it a wild stab in the dark.
 

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Warp said:
You can fill part of it to control the where the equalization happens... It could be just a small groove to allow for equalization at full travel, like it happens on a Fox shock.

I'd like to have one at hand and see for myself. I'm just giving it a wild stab in the dark.
You would have a heck of a hard time trying to fill in the dimple with JB weld. It is fairly small and it's fairly far down in the tube to be grindiing or filing. You would damage the tube right quick. You'd be better off trying to make a whole new cartridge tube. I tried to take a pic of the dimple the other day but the cam wouldn't focus on the dimple.
I found the ultimate fix for my 07' SL ATA. I replaced it with the 07' 66RC2X!
 

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Renegade, you completely rule. I will have my springs tomorrow. I will try this on my All Mountain 1 SL. Thanks for the sweet write up.

I won't be taking pictures, but I will post my conclusions.
 

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Renegade said:
Wormvine, we're speaking about the large groove on the inside wall of the main cartridge body, upper portion, not the dimple on the lower shaft.
Thats the groove, I am talking about. It's on the inside of the main tube about 1"-2" from where the hex nut screws into the tube. Mine was far from a large groove. Mine looks more like a small oval divot. There's no way in hell anyone could modify that divot and not cause some damage or drag to the main piston o-ring. The divot is not that deep. It doesn't even show on the outside of the tube.

Anyway, what would be the point. It's vital to the pos/neg setup.
Here's a completely different thought. What about removing the stop ropes on the floating piston. You would def have to experiment but it might do something interesting. I can't see it causing any harm.
Anyway you said it yourself, It would be better to have a cartridge without the "groove".
Then the neg chamber volume adjust would work properly.
 

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Discussion Starter · #18 ·
Wormvine, I'm a couple steps ahead of you. I have tried using the PAR piston with two different length tether cords; one that made the PAR chamber half of the stock size, another length of cord that cut the chamber size to one quarter it's stock size. In borh cases, I still couldn't get full travel, but it did change when in the stroke the bottom out resistance entered the picture. I'm back to no PAR piston at the moment,
 

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Renegade said:
Wormvine, I'm a couple steps ahead of you. I have tried using the PAR piston with two different length tether cords; one that made the PAR chamber half of the stock size, another length of cord that cut the chamber size to one quarter it's stock size. In borh cases, I still couldn't get full travel, but it did change when in the stroke the bottom out resistance entered the picture. I'm back to no PAR piston at the moment,
Interesting to know!. It's cool to experiment. I wish I had the ability to machine stuff. I did fabricate a cool aluminum brake hose mount for the 66. It holds the hose away from the fork and works awesome. Thankee for my dremel. The stock one is a major POS.
Thanks for all the info. Now if you could just dig into the RC2X! :D
 
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