Planet Minis

Marzocchi Fork Seal Replacement

Here’s my contribution to planet mini’s for all the info gained on this site (good and bad haha).

Anyhow, changing fork seals on the Marzocchi 35mm forks (and any other fork for that matter, is really quite easy. The tutorial below is good nuff to get you by on just about any fork, just use a small amount of common sense, and you’ll get it.

Tools needed:
Impact gun/wrench
6mm allen drive that fits your impact.
10” Crescent
Wrench (size will depend on the cartridges in your forks)
Large Screwdriver
Med/small screwdriver
Optional thick steel putty knife (see below)
Optional teflon or scotch tape
Some wire or
Optional flexible retriever tool
6” of 1-1/4” PVC sched 40 pipe split in half lenghtwise
5 gal bucket to make things easier

The basics:


These are KTM forks


Use the 5 gal bucket to hold the forks, catch any oil and generally make the process easier. Start by unscrewing the top cap and lowering the upper slider.


Next push the spring down and get a wrench on the nut below the top cap. This part takes some dexterity and a little patience. This is where your wrench size will depend on your cartridge. These are the stock KTM cartridges. In this case a 14mm wrench. The adjustable units are larger. Some are 17 some are 19. Just depends on what you have. You can use a second crescent as well.


Holding the wrench, use your crescent wrench to unthread the top cap from the damping rod.



Now turn the fork upside down to drain the oil out and find the allen bolt in the bottom. You have to use an impact to remove the bolt. Otherwise the cartridge inside just spins and you won’t make any progress at all.


Cartridge removed. Put the cartridge in the bucket and pump the remaining oil out. Carefull where you point the holes!


Next, remove the dust seal from it’s seat. This is where the putty knife comes into play. If you use a putty knife with the leading edge filed and smoothed, you will avoid damaging the lower lip of the fork tube. In this case, the previous owner of these forks butchered the tubes by using a scwerdriver like I am. Use the right tool for the job! A screwdriver does work, just be really carefull and take your time. I am going to discard these tubes, so I used a screwdriver to show what will happen if you are not carefull. See below.



Next use a smaller screwdriver to remove the seal retaining ring clip. Be carefull not to scratch the lower/inner fork tube. If you scratch it, the seals will get eaten up and you have essentially ruined your forks. Just be carefull and patient. Don’t scratch the tubes with the ends of the retainer clip ring either!



Now firmly grab the tube and the axle lug. Yank on the lug and push away on the fork tube. Do this something like a slide hammer. 2-3 good whacks and the tubes seperate. Don’t worry about the noise the parts make, it won’t hurt anything.



Now remove the oil seal. Be very carefull not to crush the lip of the fork tube. It would be best to place a thick piece of cardboard or something under the screwdriver. This is what happens when you don’t.



Next remove the upper slide bushing and remove the old seals and retainers. Make sure you are paying attention to the order of the stack!!




Next wrap the lower edge of the bushing groove with some scotch tape or teflon tape if you have any. If you dont, you risk cutting your new seals when you put them back on!

Now re-insert the inner tube in the outer tube and push the oil seal in as far as you can with your fingers. Now use the 1-1/4 PVC as shown to drive in the oil seal. A drop of fork oil or WD spread around the outer surface of the seal helps it go back in. You can usually just press it in. If needed be carefull and tap in the seal using the slide hammer technique.




Now press the dust seal back in.


Unless you have dual adjust cartridges, re-assbly from here should be a no brainer since you have gotten this far. Use the impact to re-assemble the cartridge in the fork. For dual adjusters see foot note below.

Now, with the fork collapsed and the spring out, put in your oil. You have to continue to pump the cartridge and add oil until you have added the proper amount. The amount will depend on your personal preferrence as long as it covers the top of the cartridge body plus. The more you add, the more air spring effect you will have.

The next part is a bit tricky. If you dont have a flexible retrieval tool,you can wrap a wire around the damper rod and fish it through the spring as you slip the spring in. If you have a retrival tool, just slip in the spring, then use the tool to grab the damping rod and pull it up. Either way, you have to re-install the top cap in the same fashion as it was removed. Tighten the damper rod to the top cap, but don’t over do it!


After the top cap is on, thread it back into the tube. DO NOT OVER TIGHTEN! The cap does not have to be real tight. Just snug it up with the crescent.

Your DONE!!

Foot note for dual adjust cartridges:
Dual adjust cartridges have a two piece bottom bolt that serves as the adjuster and the retaining bolt. There is only one way to get it put back in. Slide the adjuster toward the bottom of the bolt till the o-ring remains just inside the bolt. Now, with the cartridge in the tube, and the tube upright so the cartridge is at the bottom of the tube, thread the adjuster portion of the bottom bolt in till it starts to thread. Then use a small screw driver to seat the adjuster all the way in. Don’t over tighten and the o-ring has to stay in the body of the bolt as you do this. Now push the bolt up till it is ready to begin to thread into the cartridge. It probably wont start treading because the o-ring resistance will spin the cartridge. Now, with the adjuster seated and the bolt ready to thread, tighten the bolt with the impact. You should replace the o-rings while you are dong this and it may take a couple of tries to get it. Patience!!!

scottiedawg66

if you still have the old seals handy, or can measure your forks can you give me an idea of the dimensions of the marz. fork seals. I need to replace the seals in the DNM forks I have but cant find the seals. Thinking the marz. ones might work. THANKS GOOD WRITE UP!!!

mo' tarded

The marz seals are 35mm ID. 42 OD 10mm thick. I think the DNM tubes are 38mm?

scottiedawg66

THANK YOU FROM ANOTHER 625 (x) owner!!

Ktm640

Motarded on the photo and your mock up of the order of how to put washers and seal and bushings in you have got the washer the wrong side of the oil seal.

so on photo 17 from the bottom of the fork it should be

Dust seal / seal retaining clip / oil seal / metal washer / bushing

otherwise your bushing will cut into your oil seal.

trackstar

Ruh Roh

316hepster

quick question... Is it necessary to remove the cartridge (the 6mm hex bolt part) to change the seals? Or, can I just leave that part alone, since I'm not changing anything invlolving the cartridge? I don't have access to any impact tools.

fiveho

Exactly. the thick washer goes between the red oil seal and the bushing. during disassembly, if the washer is in the right location, when you "slide hammer" the inner and outer tubes apart, all of the bushings and oil seal will come out with the inner tube. you should never have to pry an oil seal out.