48mm Marzocchi warning!

STM Suspension

STM Suspension

New member
Not to be dramatic, but don't open this fork up to change the inner chamber oil unless you have a special tool to get it back together. The piston band is a flat piece bent around the piston, ala the WP twin chamber fork- but the piston is a little bigger so that tool doesn't work. The KYB/Showa forks it's based on use a circular piston band that stays on the piston...

Feel free to open them to change the springs, but beware about the inner chamber.

Beyond that, the fork looks like it'll give us a good starting point.
 
Les told me about this, had to make a tool to hold the band in place. Sounds like a tube to just slide over the piston. I want to be able to service this fork so I guess I'll have to do the same.

Whats interesting is that when Evan Yarnall from Solid Performance reviewed the fork on his bike, upon disassembly he found the band cut and a piece lodged in the rebound piston. What does that say?
 
I do not understand, I opened the inner chamber yesterday, no problem.
Tonight I will clean and refill with fresh oil, so when do you mean that I need a special tool?
If I want to replace the piston band?
 
GMP said:
Les told me about this, had to make a tool to hold the band in place. Sounds like a tube to just slide over the piston. I want to be able to service this fork so I guess I'll have to do the same.

Whats interesting is that when Evan Yarnall from Solid Performance reviewed the fork on his bike, upon disassembly he found the band cut and a piece lodged in the rebound piston. What does that say?
Click to expand...

There are numerous piston band designs that are essentially flat strips wrapped around the piston. The ends usually interlock with some sort of finger or the tapered ends join. The design itself lends to easy production and with careful assembly it works great - broken off pieces not so much.

Think of a piston ring compressor, or a nylon guide similar to what you get with Synergy seals - either will work to get things going.
 
I'm thinking its something you can easily make up from some thin plastic sheet formed into a tube. I'll have to actually see it first.

Is there a correct procedure for refilling and reassembling the inner chamber documented anywhere? Its different with the PFP correct?
 
Hey. Sorry. Meant to do this last night. Didn't mean to tell you not to open it then not show you what's inside...

We opened one up for our new test rider, Brad Hendry, to get it working better for him. He had complained of blowing through the stroke both front and rear. We installed more appropriate springs for him as well as changed the compression, mid valve, rebound and fluid for him.

I just got off the phone with Marzocchi USA (we deal directly with them for seals and parts). Let me look over it and see what we can glean.

I took a couple of pictures while I was there. The first one shows the piston band in question compared to a typical KYB type rebound piston. On the whole a pretty nice fork.

http://www.stmsuspension.com/photos/
 
As far as fluids, the guys at Marzocchi USA didn't have a lot of good info yet...

I'm running about 210cc in the inner chamber. The outer chamber I usually run between 300 and 350cc depending.

The issue I'm finding is that the Zoch doesn't have a 'blow off' port like the KYB and Showa, so if you put too much oil in the inner chamber it's going to ride harsh- just the same as if you turned their new adjuster on the top- which just adjusts preload on the IC spring. And a 22mm 12 point socket turns that thing just fine. I just held the socket in my hand and was careful and it worked great.

Please be careful working on this stuff. Replacement parts aren't so easy to come by. And while we may be looking into making some parts for the inside to get them to work a little different, they're not made yet.
 
This is what I did:
Unscrew the top nut.
Drain the oil from the outer leg.
Remove the bottom nut.
Remove the inner leg from the outer leg.
Open inner chamber, remove the compression plug and drain out the oil.
I cleaned everything with "quickclean".
Then I did this:
Filled in the new oil, put back the compression plug and verified that it ran out some oil out of the holes in the black part.

Is there any space that can expand in the inner chamber? So that you can have different amounts of oil?
Seems strange, I felt that the amount of oil that did not place in the inner chamber was squeezed out when I turned back the compression plunger.
 
So what your saying is that the oil level is esentially limited by the overflow through these holes when filled and the floating piston is inserted? That makes sense to me. I remember Evan saying that the preload on the PFP spring should be 7mm when assembled with the adjuster turned all the way out. That should be easy to measure and verify I would think.
 
I talked to the company that fixes the suspension to one of the GasGas riders in Sweden.
They do this with his Marzocchi fork:
280ml in the outer leg.
190ml in the inner leg.
5w oil.
They also said that the excess oil in the inner leg is pushed out when you put in the compression plug.
 
STM Suspension said:
Not to be dramatic, but don't open this fork up to change the inner chamber oil unless you have a special tool to get it back together. The piston band is a flat piece bent around the piston, ala the WP twin chamber fork- but the piston is a little bigger so that tool doesn't work. The KYB/Showa forks it's based on use a circular piston band that stays on the piston...

Feel free to open them to change the springs, but beware about the inner chamber.

Beyond that, the fork looks like it'll give us a good starting point.
Click to expand...

Pictures would be great to look at if you have any
 
I think that everybody have to email Marzocchi (and GasGas) asking about the manual and parts.
 
I have e-mailed at least 5 times to Marzocchi and asked about the manual.
No response ....
I have also mailed to GasGas, no answer ....
 
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