Marzocchi Marathon S Forks

[JackN]

I've rebuilt a set of these air sprung oil damped forks, i.e. powder coat, new seals and new Schrader valves. The +ve and -ve air valves are recessed into the fork leg caps.
I've bought an adaptor (not O.E.M as these are unobtainable) and this works fine on one side. The other leg has an offset +ve and a central -ve valve. I cannot get air into this leg at all. The adaptor doesn't reach far enough in to depress the top of the valves.
Has anyone come across this problem and solved it or can anyone offer any advice? They look like decent forks and I'm trying to keep the spiralling (upwards) cost of this rebuild, 1999 Marin Mount Vision down L.O.L. Thanks.

 

[scottproonly]

Re:

Can you not use some kind of valve extender meant for a car valve?
Kes

 

[Mike Muz]

Re:

I have a pair or Marathons on the 29er in my sig.
Two valves on the left leg,one on the right. Is that what you have?
Have you got a photo of the adaptor?

Mike

 

[twain]

pics will help - signing up to this as its intriguing me....

 

[magas]

maybe one of those adaptors will fit; or thats the one you are allready have ?

https://www.bike24.de/p14689.html

 

[JackN]

Re:

The screw in cap at the top of one fork leg has a central recessed valve and an offset recessed valve. The offset is for +ve air (compression)and the central is for -ve air (rebound speed.) The other leg has one central recessed valve for +ve air.


I have the "Marzocchi" adaptor i.e. the metal tube with a threaded ends one of which has an O ring to seal the valve recess when it's screwed into the as sold by Chain Reaction, Wiggle Ebay etc.

It screws into the recessed hole and it is supposed to depress the Schrader valve and when the shock pump is attached this lets air into the leg. However, the adaptor only works on the leg with the single valve, on the Marathons that I have this is the ETA side. The fork works under compression and springs back no problem. But I cannot get air into the other two chambers.

Also the pressure required is low, for my weight about 37 p.s.i/2.5 bar. My shock pump is too insensitive at these low pressures.

The Schrader valves I have are brass ( I think) I may attempt to solder some solid copper wire to them to increase their height so that the adaptor can push them down. Or, a short (very short) length of stiff plastic tubing pushed/glued to the valve may work. I've got the red WD40 tube in view for this.

There is a detailed illustrated stripdown and rebuild of the Marathon S on the Enduro seals website (URL below) Section/picture no 61 is my problem part.

http://www.enduroforkseals.com/id27.html

 

[02gf74]

Does the adapter you have screw in or is a push fit, and how does it seal?

What is stopping the adapter going in further so it presses on the valve core stem?

There aew different length valve cores, can you not find one with a longer stem? Remove the core and go to your local car tyre garage/shop.

Else you need to fit an extension to the stem, a small tube like you suggest, note cotton ear buds are usually on the end of a hollow plastic tube that i reckon is closer in size than wd40 tubeyou suggest.

 

[JoeG]

http://www.marzocchi.com/Template/listM ... 9&offset=1

 

[JackN]

Re:

Thanks for the help/suggestions. Apparently Rockshox made some forks (Duke/Psylo?) with similarly recessed valves but soon altered the design to use exposed valves under aluminium caps.

After a little head scratching I think I've solved it. The screw in adaptor doesn't reach the pin on the valve. So, I loosened the valves to make them reach the adaptor. After a few attempts I was able to inflate the forks, remove adaptor/pump tighten the valve fully and had working forks.

It's not an ideal solution since it involves much trial and error i.e unscrew the valve too far and when the adaptor/pump is removed the leg deflates. But it works. I shall try and extend the valve, thanks for the cotton bud tip I'll have a look at that.

Quite simply the adaptor needs to be longer at the end that screws into the valve recess. There are a number of different ones available so I guess it's just a matter of chance if you get the correct one. On with the build.