Fork rebuild

[Francis Chartier]

Those 40 Marzocchis don't have a compression damping as you might have seen on other forks. It's only some sophisticated sort of bottom out protection.

The compression damping works only on the last 20-40mm or so.

 

Hubert

 

They have compression damping... of a sort.

More precisely, they have crappy compression damping.

 

There is a "needle" inside the hollow main rod, inside the fork cartridge, just above the cartridge piston.

That needle is pushed on a conical seat by the adjustment rod (it slides in the main rod) under the screw in the top nut of the fork.

 

When you turn clockise that screw, the needle is lowered on the seat and close the oil bypass from under the piston to the top of the cartridge, augmenting the compression damping as the piston travels downward.

Counter-clockwise, the needle/seat clearance is augmented, thus reducing damping (more oil flow).

 

Well, that is the theory, then Luigi strikes...

 

The seat of that needle collects oil crud and the neddle then get stuck very quickly in the closed position, closing the oil bypass and setting to maximum the damping compression. It is easy to verify: remove the wheel and axle, remove the top cap and the blue nut, then the spring so you can pump the rod/piston assembly in the cartridge.

 

When you push the rod/piston downward, the oil going through the oil bypass should push the neddle up, and you should see the adjustment road climbing outside the main hollow rod, 3/4 mm. If the needle is stuck it will not climb and the move of the assembly is slowed.

 

What can we do?

 

Disassemble fork, rinse with cheap oil, clean thoroughly, rinse, reassemble with fresh oil.

Yo! problem solved... for 500/1500 km, YMMV

 

I think that the design and the manufacturing of the Marz 40 is crappy and you'll have to replace the cartridges with decent ones (Maxxton or others).

 

My solution: trash the original MarZocchi 40 USD and swap for a brand new Paioli USD41 SuperSport bought cheap from the Voxan factory (leftover from the 2001 Cafe-racer model, upgraded now with a bigger fork).

 

http://www.paioli.com/paiolini/detail_en.php?id=67

 

Hope this help.

 

--

Francis

[GuzziMoto]

Maybe your forks are different then the ones on my wifes '01 V11. But increasing the damping in the initial part of the stroke acually smoothed out the ride. Before it just blew thru the stroke and slammed into the stiff part at the end. Now it is more controlled. Try putting a zip tie around your inner tube on one leg to measure fork travel. When I did that I found that even on a smooth road it was using most of the travel. While I don't think you should just blindly do what I(or anyone else) says, I do encourage you to experiment with your forks. I put mine back together with no springs and you could see what the damping was doing without any trouble. Good luck.

[BrianG]

I fixed mine by adding Traxxion Dynamics cartridges.

[luhbo]

....

 

My solution: trash the original MarZocchi 40 USD and swap for a brand new Paioli USD41 SuperSport bought cheap from the Voxan factory (leftover from the 2001 Cafe-racer model, upgraded now with a bigger fork).

 

http://www.paioli.com/paiolini/detail_en.php?id=67

 

Hope this help.

 

--

Francis

 

Interesting, thanks for the link.

 

@GuzziMoto

I think I'd first make an experiment with stiffer oil in the left leg. I'm still a bit skeptical about closing one whole...

 

Hubert

[Guest ONETHUMPER]

Just a quick update on the forking problem. Using the information from you guys the forks are fine. I pulled things apart and it is true the main part of the compression comes in at @ the last 20% of the travel. When the blue nut is adjusted at 22mm the compression adjuster screw still does not do much until almost fully compressed. But, by adjusting the length of the spacer it's working great. I cut 1/2 inch from the spacer I had made. Using the old spring and spacer I cut the new spacer to equal the length as it was, the new spring is a little smaller but is a 1.1 spring. And let me say that the front suspension of this bike is great when set up properly, just my 2 cents worth, and again thanks guys!