40Mm Marzocchi Forks Disassembly (And Hopefully, Reassembly)

[mr neutron]

Hey, All!!!

I've got a 2010 280 Pro TxT with the 40mm aluminum Marzocchi forks I'm working on. Wasn't too sure the videos at Gas Gas USA were "relevant" for these forks, so that's why I'm posting here......

I started out doing (what I thought was...) a simple oil change of the forks. I took the fork legs out, after loosening the caps. Removed the caps, springs, & spacers, and then turned each fork leg upside down in an oil drain pan, and let them sit that way over night. The oil looked thick & yuckky. Not much yuccky oil came out, but so far so good?

Next day, I thought while these forks were this far apart, I'd see If I could get my previously stuck rebound adjuster to turn. I managed to, and actually unscrewed it out. I turned that Rebound side fork leg upside down over the drain pan, pumped it & the cartridge a few times, and got oil to come out of the cartridge rod. I didn't do this to the Compression side, because the adjuster worked.

Put oil in, set the level to 160mm, re-assembled the bike, and went for a test ride. I now have no rebound, and seemingly no compression either. The adjuster on the compression side turns, but it now has essentially no effect at all. The bike tops out harshly, and bottoms out much easier now than it used to.

I've done some reading here, and in this thread, member Michael Martin states that the cartridge needs to be removed to filled after an oil change.

http://www.trialscen...nge#entry272977

I'm willing to try this, but wondering "why?". How do these forks come apart? I'm betting most likely that I'll need to pull the dust seal and a circlip to remove the top leg from the bottom half, and pull the allen head bolt out of the bottom leg to remove the cartridge? Will the oil seal & bushing come out with the upper fork leg, like on other bikes I've worked on?

I guess, in a nutshell, I'm asking how these forks come apart, and what to watch for on re-assembly......

It's funny, I've worked on, rebuilt, shimmed, and bled my old KTM WP 50mm Extreme forks & twin piston PDS shocks for myself & a friend, and did routine stuff on my '06 YZ450's forks & shock. But to have my butt kicked by these forks is kinda frustrating. One nice thing about the bikes/suspensions mentioned above is that there's a lot of info out there about those forks.

Thanks for any help/advice/warnings you all may have!

Jimmie

[lineaway]

Did you read step #3. Make sure no air is left in the system?

[lineaway]

To answer the question, all zoochi`s come apart the same. The `09 had a cartridge change.

[mr neutron]

Thank you, Lineaway!!! That helps a bunch! I hope New Mexico never runs out of rocks or places for you to ride!

I do have one question though.... "Did I read Step #3" of what????

Jimmie

[jse]

Thank you, Lineaway!!! That helps a bunch! I hope New Mexico never runs out of rocks or places for you to ride!

I do have one question though.... "Did I read Step #3" of what????

Jimmie

If you are going to work on forks a lot, you may consider making a bleeding tool. It's steel tubing with a nut welded on the end and a bleed hole drilled. It's threaded on the cartridge rod and allows you to easily pump the cartridge to work any air out. I made these tools that have various size nuts to fit a wide variety of forks. They also make assembly easy as you can pull the cartridge rod up after putting in the spring, washers and spacers.

Jon

[mr neutron]

Jon,

Thank you for replying, and for the pics of the tools you came up with! That's a really great idea for the bleed tool you came up with..... It would work out much better than my piece of copper wire that I use to pull the rod up.......

Now, for the inevitable questions:

Is it "normal" that my seal and the bushing for the lower tube stayed inside their counterbore in that lower tube? They didn't come out with the upper tube, as the video showed for the '07 & earlier forks. My upper tube simply pulled right out with only it's bushing; no "slide hammer" action needed to get the forks apart like was necessary on other forks I've worked on. Kinda like the old damper rod forks, ya know? Theoretically then, all that holds the upper & lower legs together would be the cartridge, essentially, by the allen bolt on the bottom by the axle, and the upper cartridge rod that screws into the fork cap? Added in EDIT: I can pull my upper tube out of the lower one with the seal, washer, clip. & even the dust seal intact. I read about this seal & bushing staying in the lower fork leg in another post/thread as well, so this isn't the only time this has come up. It doesn't seem right.......

The compression-side cartridge is full of holes along its side, like most others I've seen are. This has also been another source of confusion for me, when combined with this post in that thread I linked to in my original post:

Michael Martin, from 6/9/11:

Remove cartridge from fork, disassemble cartridge, fill with fork fluid, reassemble cartridge, then put cartridge back in fork tube, then with fork and damping rod completely depressed set oil level 160mm from top of fork tube. Cycle damping rod to make sure no air is in cartridge and check oil level again. Pull up damping rod and insert spring and preload spacer, screw on fork cap.

I must not be understanding his intent. This would seem impossible to do, as fluid would leak out everywhere...... What worked best for me, in an "experiment" was to bolt the cartridge into the lower fork leg from the bottom (by the allen bolt/copper washer). Then, I filled the fork leg up with oil, and pumped/cycled the cartridge damper/"hydraulic" rod up & down a couple of inches, until the action smoothed out. Then, I slid the upper leg into the lower, and cycled both that upper leg & the cartridge/damper rod up & down separately & together. From there, a person would fill the thing up to the 160mm level, reassemble, and etc...... Is this "sound" logic? How do most of y'all do this? Is it necessary to pull the forks apart like this everytime you simply want to change oil?

Also, my owners manual shows my 160mm oil level dimension, with the fork tube compressed, and the damper rod "out". It also mentions to "Measure without the pier and the hydraulic rod extended", What's a "pier"?? The spring???

Jimmie

Edited November 25, 2013 by mr neutron

[jse]

Is it "normal" that my seal and the bushing for the lower tube stayed inside their counterbore in that lower tube? They didn't come out with the upper tube, as the video showed for the '07 & earlier forks. My upper tube simply pulled right out with only it's bushing; no "slide hammer" action needed to get the forks apart like was necessary on other forks I've worked on. Kinda like the old damper rod forks, ya know? Theoretically then, all that holds the upper & lower legs together would be the cartridge, essentially, by the allen bolt on the bottom by the axle, and the upper cartridge rod that screws into the fork cap? Added in EDIT: I can pull my upper tube out of the lower one with the seal, washer, clip. & even the dust seal intact. I read about this seal & bushing staying in the lower fork leg in another post/thread as well, so this isn't the only time this has come up. It doesn't seem right.......

***Not unusual. The pliable seal and dust cover will allow the tube bushing to slide through. I always use a little heat from a propane torch (a good heat gun will also work) on the upper part of the lower tube to break the bond the seal normally sets within the tube. It should come out easily. A propane torch is a regular tool of a good suspension tech.

The compression-side cartridge is full of holes along its side, like most others I've seen are. This has also been another source of confusion for me, when combined with this post in that thread I linked to in my original post:

Michael Martin, from 6/9/11:

Remove cartridge from fork, disassemble cartridge, fill with fork fluid, reassemble cartridge, then put cartridge back in fork tube, then with fork and damping rod completely depressed set oil level 160mm from top of fork tube. Cycle damping rod to make sure no air is in cartridge and check oil level again. Pull up damping rod and insert spring and preload spacer, screw on fork cap.

*** Mike's got it right (I know Mike and he knows his stuff). The problem with this design of Marzocchi forks is that, because of the internal valving, the cartridge does not completely bleed down so the oil must be set by level, not volume. It's a much more accurate measurement and a good suspension tuner will never use volume, only level. The trick is in the bleeding proceedure (it may take some time and make sure the cartridge below the oil level, which is why Mike says set oil level and then bleed cartridge of air) and remember, each cartridge will feel different: the "rebound" side will offer little resistance when the damper rod is pushed in and the compression damper rod will offer little resistance when the rod is pulled.

I must not be understanding his intent. This would seem impossible to do, as fluid would leak out everywhere...... What worked best for me, in an "experiment" was to bolt the cartridge into the lower fork leg from the bottom (by the allen bolt/copper washer). Then, I filled the fork leg up with oil, and pumped/cycled the cartridge damper/"hydraulic" rod up & down a couple of inches, until the action smoothed out. Then, I slid the upper leg into the lower, and cycled both that upper leg & the cartridge/damper rod up & down separately & together. From there, a person would fill the thing up to the 160mm level, reassemble, and etc...... Is this "sound" logic? How do most of y'all do this? Is it necessary to pull the forks apart like this everytime you simply want to change oil?

*** I always bleed the cartridge with the upper and lower tubes assembled and seals installed. You should bleed the oil covered cartridge full stroke, otherwise there will be trapped air in the upper part of the cartridge.

Also, my owners manual shows my 160mm oil level dimension, with the fork tube compressed, and the damper rod "out". It also mentions to "Measure without the pier and the hydraulic rod extended", What's a "pier"?? The spring???

*** To my knowledge and experience, oil level is normally set with the upper tube collapsed into the lower tube and the damper rod pushed down into the cartridge. It would make a slight change in volume (over the rod pulled out) to compensate for the part of the rod that extends into the oil if the rod were pushed in. The problem may be in the Spanish-to-English translation as "Measure without the pier and the hydraulic rod extended" may also be taken as "without the pier and without the hydraulic rod extended" (I'm also guessing that "pier" is the spring). To confuse "pier" with "spring" brings up the possibility that sentence structure is also suspect. Jimmie, I think you have a Dirty Harry situation here, as in "how lucky do you feel?"....... Personally, I would collapse the rod down as the recommended oil level is really just a starting point for accurate tuning for weight and riding style. Incidentally, those cryptic directions are a recent addition to the bottom of the oil level chart, they are not in earlier Owner's Manuals.

Jon

[mr neutron]

Thanks again, Jon!

Okay, well, it's good to know that things are fairly "typical" then; that's a relief for me.

I do indeed have an electric heat gun I used when I planned on separating the two halves of my fork. That thng comes in really handy, for a variety of things.

Before it cooled off a little here, I put some old suspension fluid I had in the barn in that compression side fork. Everything seemed to work fine while bench checking it. The adjuster made a noticeable difference, motion seemed nice & "restricted" when compressing, & etc.. Thanks for all your help, Jon & Lineaway! Hopefully, will get the other side done in the next day or so. I have to patch up some minor rock dings in the upper legs first, though. Is that typically done with nail polish & 600 grit sandpaper?

After I think about it, really, the only way to do a decent job of an oil change IS to disassemble the forks like this, in order to flush out the old fluid with solvent. And the oil in my forks was somewhat more like a chocolate milk shake than suspension fluid, hee hee.....

Oh, yeah. I was wrong about the diagram in my User Manual (page 30, 2010 TXT-PRO). It DOES NOT show the damper rod extended, like I said above. My mistake there. Sorry about that.

Again, thanks for your help!

Jimmie

[lineaway]

Glad you have it straight in your head now Jimmie. All this talk reminds me that my sons fork has a slight seep.

[jse]

Thanks again, Jon!

Okay, well, it's good to know that things are fairly "typical" then; that's a relief for me.

I do indeed have an electric heat gun I used when I planned on separating the two halves of my fork. That thng comes in really handy, for a variety of things.

Before it cooled off a little here, I put some old suspension fluid I had in the barn in that compression side fork. Everything seemed to work fine while bench checking it. The adjuster made a noticeable difference, motion seemed nice & "restricted" when compressing, & etc.. Thanks for all your help, Jon & Lineaway! Hopefully, will get the other side done in the next day or so. I have to patch up some minor rock dings in the upper legs first, though. Is that typically done with nail polish & 600 grit sandpaper?

After I think about it, really, the only way to do a decent job of an oil change IS to disassemble the forks like this, in order to flush out the old fluid with solvent. And the oil in my forks was somewhat more like a chocolate milk shake than suspension fluid, hee hee.....

Oh, yeah. I was wrong about the diagram in my User Manual (page 30, 2010 TXT-PRO). It DOES NOT show the damper rod extended, like I said above. My mistake there. Sorry about that.

Again, thanks for your help!

Jimmie

Jimmie,

On fixing the fork tube "dings", I use superglue with good results. Just make sure the scrape is very clean and free of any oils. I have a short piece of 1/2" machined bar stock (very hard and very smooth and very level) that I wrap the 600 grit wet/dry around. Be sure to sand "around" the tube and not in one place so you don't get a flat spot.

Jon

[mr neutron]

Hey, All!!!

Thought I'd try to do a quick update on the status of my fork oil change odyssey. I tend to be wordy, & I apologize for that, but I'll attempt to be concise here.....

First of all, I've discovered I have a recessive Stupidity Gene that seems to kick in everytime I attempt to pull any maintenance (or ride) on this bike. I did indeed misread & misunderstand Michael Martin's post, as well as others in that thread I linked to above. Sorry to all for my confusion. His post pretty well nailed it, and further reading of other posts in that thread helped a lot......

The compression side went well, other than the forks not exactly coming apart like the video showed, and like other conventional forks I've taken apart in recent history.

Getting the rebound cartridge apart was a little more difficult on my bike. I think I bought a rebound cartridge that was possibly built on a Monday morning, or something.... Is Marzocchi's quality sometimes sorta "questionable"? (I work as a machinst making aviation parts, and we work hard not to let parts out of our areas like I saw inside this cartridge....) There were numerous gall marks at the bottom of the cartridge, where the circlip and lower aluminum plug go. Then, there was a half round gouge or ridge up inside the tube about 4 inches or so from the bottom. These things combined to make it very hard to get the 2 aluminum "plugs" (spring in between these) out that seal the lower end of the unit, which again had me baffled. I took the cartridge to work and ran a hone through the inside a few quick strokes, and that smoothed that out a bunch. I deburred the 4 holes near the bottom; they had some nasty burrs leftover from drilling that cut into the o-rings. The damper rod itself had a couple of dents or dings in it; I hit those with 600 grit sandpaper.

Anyway, it all went back together well, and seemed to have bled well. I did manage to "fix" my stuck & broken rebound adjuster. It actually seems to make a noticeable difference during use..... I've got a couple of short rides on it now, have made a few adjustments, and so far, it seems to be working well. No leaks to report, also. (That SuperGlue fix worked well, Jon! )

Jon, Lineaway, or anyone that knows a bit about these forks: That second aluminum plug/piston/whatever it's called, that has the o-ring around it and the plastic hydraulic-type seal around it. NOT the one the allen head bolt/copper washer threads into from the bottom of the forks, but the one that does most of the "sealing" of the cartridge...... It has a screw through the center of it. I didn't mess with that, but is it possibly a screw for bleeding the cartridge?

Anyway, Thanks, and very much, Jon & Lineaway, for your help! And Michael Martin, if you ever read this, Thank You also!

So much for a short post, huh?

Jimmie

Edited November 29, 2013 by mr neutron

[zippy]

Mr. Neutron,

I for one, enjoy reading your posts. I like the style with which you write. but I tend to be "wordy" as well.

Good to hear the forks are back to usable condition.

[mr neutron]

Thanks, Zippy!!

I actually llike reading your posts better! They're usually much funnier!

I have to replace an o-ring in that pesky rebound cartridge. It's probably sealing well enough, but the burrs inside cartriddge did chew up the o-ring somewhat during removal. The next time I have the forks apart, I'd like to get Mrs. Neutron to take some pics of all the parts I tried to describe above. She's a way better photographer, with a way better camera. I tried taking some pics with my primitive digital point-and-shoot, and the pics kinda sucked like a bucket of ticks..... Anyway, photos would probably make more sense than my verbal descriptions.

Hope y'all had a Great Thanksgiving! I'm pretty sure my bike needs new. stiffer springs after eating like an idiot yesterday!

Jimmie

Edited November 29, 2013 by mr neutron

[michael martin]

In moments of someones confusion I always like to be the subject of even more confusion. Haha... Very happy it helped you Jimmie. I find it best to use a top quality synthetic cartridge fluid because those forks tend to dirty the oil pretty quick.

[mr neutron]

In moments of someones confusion I always like to be the subject of even more confusion. Haha... Very happy it helped you Jimmie. I find it best to use a top quality synthetic cartridge fluid because those forks tend to dirty the oil pretty quick.

Michael,

Thank you so much, both for your response just now, and for the one I linked to above. Thank You! Once I pulled my head outta my a$$, it all became pretty clear. Guess I typed & posted first, and then took the time to think.....

I normally do use synthetic fluid; Red Line in this case. I actually prefer to run the really light fluid viscosities, in the winter and summer. The lighter fluids all seem to have the higher centistoke ratings, and in my old KTM, they just seemed to stay more consistent & last longer.

But the shim stacks in these 'Zokes seem to be meant more for the heavier fluids, like 7.5 wt. or more. If a (Heavy ) person wants to run the thinner fluids, it would seem making a stiffer shim stack would be in order? My rebound stack has (2) 20mm dia. shims X .11mm thick, and a 13mm dia. X .16 thick backer. To use the thinnner fluids, would a slightly bigger diameter backer shim, say, around 16mm, help in that respect?

Maybe I should buy another treadmill instead......

Jimmie