Fuente: EmanResu en forums.mtbr.com:
http://forums.mtbr.com/shocks-suspension/operation-fox-dhx5-air-bleed-491668.html
Howdy folks. I bought a DHX5 that had a lot of air in the damping circuit so decided to dive in and sort it out. I came across some good info online that other folk had put up though much of it was for the coil version, and the air appears a little different in that it's inverted by comparison and thus slightly more involved because of an additional shaft volume and orientation issue. I'd read beforehand about the possibility of submerging the entire unit in oil to do this but I didn't have this much oil around, and also didn't really want to have to do it that way, so I came up with the following...
Whether there be better ways to do this I don't know (in hindsight there are likely a number of possible methods), but can say that the following worked well for me and required very little oil and only basic tools to complete. So, for what it's worth, here are a bunch of images and short descriptions of what I did;
Las primeras cuatro imágenes simplemente muestran las piezas del amortiguador desmontadas y limpiadas convenientemente antes de comenzar el proceso. Algunas partes no se muestran pues las quité para limpiarlas. Aside from the main air piston seals I'd also removed an o-ring from the bottom out adjuster to make things a little easier further on (not essential).
Para usar una cantidad mínima de aceite en el proceso de sangrado, usé una botella vacía de pastillas con el fondo cortado y con una banda de foam colocada en el cuello de la botella para permitir deslizar/sellear este depósito casero a través del émbolo principal.
Clamping the assembly upright using my truly amazing vice + plastic chair. Nothing but the highest tech here...
1. Engrasando un o-ring para tenerlo preparado para su montaje.
2. Con el pistón flotante extraído de la cámara secundaria, en este momento introduzco en el sistema tanto aceite nuevo como me es posible. Con esto conseguimos inundar realmente toda la cámara secundaria y vías de aceite para ayudar con el sangrado posterior.
Sin montar de nuevo el pistón flotante, cerramos la cámara secundaria, enroscando a mano. Una vez hecho vertemos aceite en y sobre el pistón principal, de manera que ambos lados estén tan llenos de aceite como sea posible. y entonces cierro la cámara secundaria con el tapón guardapolvos.
On the main piston shaft near the eyelet hay un tornillo muy útil que está escondido debajo de una pequeña bola blanca de nylon. Si se extrae esa pieza blanca aparece un tornillo de aluminio de 4mm. Lo desatornillamos y extraemos una pequeña pieza de goma que lo sella por la parte interior. Quitamos también el tapón de goma y habremos abierto la cámara del amortiguador para su posterior sangrado.
Ahora debemos deslizar the shaft en el pistón de aceite/aire, atornillarlo fuerte, y empuzar el shaft hacia abajo en toda su carrera (debemos hacerlo lentamente para minimizar la formación de burbujas de aceite/aire en el interior).
Montamos el depósito casero y añadimos el aceite. Sólo se necesita una pequeña cantidad, unos 50 cc. Llegados a este punto, es un proceso muy simple de deslizar el shaft arriba y abajo para gradualmente reemplazar el aceite nuevo del depósito por el aire del sistema.
Dediqué cerca de una hora en esta fase pulling (pushing) air out, including leaving it to settle here and there. It's very much like bleeding hydraulic brakes and is easy to get an idea of how well things are going by just listening for the obvious sound of air bubbles shifting about, and observing bubbles ejected into the oil reservoir. After a while when things were feeling nice I dialed in a load of rebound to add resistance to pulling the shaft back up its stroke. This seemed to operate similar to pulling on a syringe when doing hydraulic brakes in that (I guess) it causes any tiny air bubbles in the oil to expand and float up faster towards the top of the shaft, and thus into the reservoir. I also tilted the assembly about and gave it a tap/knock here and there to help loosen any bubbles trapped in the system. Doing all this got it to a point where I was confident it was well degassed.
1. Here I extended the shaft fully, tilted the assembly back, deslizo la reserva hacia abajo para dar acceso al tornillo de alluminio, entonces con cuidado coloco el tope de plástico en el agujero sin que se cuele nada de aire (es fácil) y atornillo el tornillo de aluminio de 4mm, para sellar el conjunto.
Now the whole lot is sealed tight and so you should have a very strong hydraulic lock assuming most of the air is out. Apenas podía comprimir the shaft -sólo 1mm-.
2. Aquí quito el control del bottom-out para acceder a la cámara secundaria de nuevo. De hecho había algunas pequeñas burbujas de aire enganchadas en las paredes de la cámara secundaria así que las desprendí con un palillo de madera. In hindsight it might be worth gently pushing the shaft into its stroke a small amount at this point to push any potentially trapped air bubbles around the ProPedal valve section into the piggyback volume, asegurándose de retornar el shaft a su posición de extensión completa antes de reinstalar el IFP.
1. Ready to reintroduce the IFP.
2. With the centre screw removed I pop the IFP back in.
1. Ahora ajusto la profundidaz del IFP a 33mm para este amortiguador de 190x50mm (2'') (based on info gleened on teh intertubes ), vuelvo a colocar el tornillo central de sangrado para sellarlo, quito el exceso de aceite y añado algo de fluido de aceite de 85w.
I'd be careful not to cycle the main shaft at this point, or at least only very gently if doing so as the piston looked to wiggle up/down unevenly (with potential to break seal) without the usual "75-200psi" pressure backing it (I presume pressure would normally keep this in check ).
2. Montando las piezas del bottom-out en la cámara secundaria y presurizando.
Viola! It's at this point I can cycle the shaft pretty hard and check to see if it at least feels alright. Good news is it felt bang on, there was no sound of air in the system at all and it all felt very slick. I'm pretty confident the procedure has worked well at this point, and so just the nice easy air can reassembly to do now.
I can confirm all feels well after completing everything and installing it on the bike. In comparison to what the unit was like beforehand it's a lot better. It's virtually silent in operation now when bouncing on the bike other than a touch of valving whistle. So damn good. I'm just glad it was all a relatively painless process that even a n00b like me could pull off with only minimal tools and experience.
Hope someone finds the info useful.
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