Marzocchi 48mm CC Forks

[Vindicator]

Originally Posted by fasteddy

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]

Originally Posted by Leo

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

Originally Posted by 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]

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]

Originally Posted by GMP

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 ...