Marzocchi 48mm CC Forks

[Vindicator]

If you overfill the carrtridge, will the excess oil be pushed out the bleed holes when inserting the comp / PFP assembly? This is confusing as Leo has said it does, and Evan Yarnell has said it does not. It makes sense that it should. Could there be differences in the forks?

I did not overfill but I can imagine it would be pushed out the bleed holes until the PFP o-rings seal the space below those holes. My understanding is that these o-rings seal the PFP and are responsible for maintaining the inner pressure, no oil should pass by these o-rings with the consequence of losing your desired PFP pre-load. I'm not sure but I think that if you overfill the cartridge you will be pushing the PFP up more than the 7mm standard pre-load Evan mentioned .
I can tell you that the more oil you add the more painful is to close the cap . I would like to see what machine they use at Marzocchi to close this cartridge

I would think that the reason one extends slower is due to less pressure, which is due to less PFP preload, lower piston position from a leak. What size orings?

Yes, I hope that's the reason . I don't know yet, I have to tear the cartg apart again

 

[GMP]

Why don't they just set the bleed hole/piston position so the correct PFP preload is acheived once the oring passes by the hole? Just like a KYB or Showa. I guess that would be too easy. So you have to get a perfect oil level for an accurate preload I assume.

Maybe check bleed hole area for a burr that could have damages oring.

 

[GMP]

I just talked to Les, he's feelin' good back at work and has done some of these lately. He agreed with Evan, its not like a KYB, you must get the oil height correct after bleeding for the right PFP preload or the cap will be near impossible to get on. Maybe thats why Leo had to resort to tiedowns to compress the spring?

 

[Leo]

I think that you have to overfill the cartridge and close it. Then push the piston up to bleed the air that is trapped inside the cartridge.
Please, correct me if I wrong.

 

[GMP]

You would think so. I'm going to call him again when I have mine apart next week.

 

[Boomhauer]

You would think so. I'm going to call him again when I have mine apart next week.

This is a good thing Glenn. I will be calling you when I get my bike. Girard & I will be changing out my fork springs & shock spring for my fat azz. I will need the inside scoop from you. I have never been inside the Zook forks.

 

[Hoobs]

Wonder if it matters what position the PFP has when assembly of the inner chamber?

 

[Leo]

PFP with 0 turns is way more easy.

 

[fasteddy]

Spring Change Out

I'm changing out my fork springs on the 48 zokes.. Anything special I need to know...


Ed....

 

[Leo]

... no oil should pass by these o-rings with the consequence of losing your desired PFP pre-load. I'm not sure but I think that if you overfill the cartridge you will be pushing the PFP up more than the 7mm standard pre-load Evan mentioned .

When the PFP piston goes too up, the oil will escape in an small recess that has in the PFP axle to this purpose. Not in the outer diameter. Just like Showas.

 

[Vindicator]

I'm changing out my fork springs on the 48 zokes.. Anything special I need to know...


Ed....

Drain the oil in the outer tube, remove the nut at the bottom of the stanchion tube , pull the cartridge and replace the springs.

 

[Vindicator]

When the PFP piston goes too up, the oil will escape in an small recess that has in the PFP axle to this purpose. Not in the outer diameter. Just like Showas.

That's right about half way in the PFP axle, correct?

 

[Vindicator]

So I dismantled both cartridges again, checked rebound valving, nothing out of its place.

A closer attention to the PFP piston showed this:

Not really sure the reason for this small hole but there's 2 more. They connect to the inner side of the piston. Pressure blow off ?

PFP inside

 

[Vindicator]

PFP spring preload max (using the 22mm) is 5mm, ~11 turns

Here with 0 preload and 0 turns

 

[Vindicator]

Here's a measurement of the 130mm oil level. In the midle of the shaft you can see the recess Leo mentioned.

coincidence or not, leaves ~7mm to be dipped in the oil

It matches more or less the amount of oil Dave from STM Suspension mentioned (http://www.gasgasrider.org/forum/showthread.php?t=11942)
Because oil can't be compressed with this small pressure (please correct me if wrong) the piston will move up around 7mm after you close the cap.

Picture of the Compression unit side to side with the cartridge

The distance from the top of the cartridge to the holes is ~55mm it's the same distance from the top to the beginning of the piston shaft

 

[Synergy-Seals]

What that hole does is eliminate vacuum. The same effect you see on lower tubes between the du bushings.
What concerns me is the huge gap between the two ends oc the du bushing......bad designing. The littl hole can be moved up or below the bushing edge outside of the bushing area.

Rob

So I dismantled both cartridges again, checked rebound valving, nothing out of its place.

A closer attention to the PFP piston showed this:

Not really sure the reason for this small hole but there's 2 more. They connect to the inner side of the piston. Pressure blow off ?

PFP inside

 

[Vindicator]

in the meantime some of the goods started to arrive

A real pain to get them in Portugal, ordered from Spain

 

[Vindicator]

Closed the cartridges, again, one still let's some oil to pass in the o-rings...while the other initially was fine and then started doing the same. I could see the oil coming out of the the holes every time I pushed the rod up and the o-ring would pass the hole.
For the moment I will leave it like this but I will replace the o-rings and PFP bushing the next time I service the forks. They now both rebound at the same time, there's still a very small difference but nothing compared to what I had before.

Marzocchi must have an hydraulic gismo to close the cartridges, I can image the strength it took Leo to close his with the overfill

I can understand now why Leo mentioned the excess would come out through the holes, it would either slip through the o-rings or from the inside of the piston (after passing the shaft's recess).

GMP, before opening the cartridges next week, could you please check if you are able to use the full range of the damping rod as opposite to what I encountered in mine ?

Please also look at the cartridge holes while you fully compress the fork and could you kindly let me know how much mm of the piston you can see passing in the hole ? Mine is about 6mm

Leo, do you remember if you could compress the forks all the way to the lock nut after you closed them ?

 

[Vindicator]

What size orings?

I measured 36mm diameter but I think there is a GG kit with these o-rings + the PFP bushing and the compression piston o-ring, #8501641/C , can anyone confirm ?

 

[twowheels]

Just knocked down a set of 30 hr old 48 Marzocchis. Lots of metal flash in the oil from the outer chamber, and only about 260cc was recovered.

The inner chamber yielded 210cc on the nose however, and the oil looked reasonably clean.

The rebound rod would stroke completely into the chamber on both sides. A little tweak to the rebound stack and a plus size on the main springs and they'll be headed back together.

Reassembly could be a bear ...