kids don't try this at home - pt.2
Okay, you're in luck.
If your willing to spend the cash, like rik said, just get it rebuilt properly dont arse around. I'm sure dirtworks will look after you. With the disclaimer over, here goes.
I'm pretty sure that the nitrogen chamber has a floating piston that seperates it from the oil, and when the oil has leaked out, well the piston will max out, ie the "chamber" will be as "large" as it can be, and that will be all. That is based on the assumption that there IS a floating piston and that the nitrogen is charged through the piggyback after rebuilding the shock with oil. I'm quite sure that's how it works, but do correct me if i'm wrong. So basically, the nitrogen will not leak out, nor leave the shock, unless the cap on the resovoir itself is opened.
Anyway, in my case, it wasn't worth rebuilding one particular shock, so I went ahead and did a DIY. Below = what I did.
1. Take the spring and all hardware off the shock. Wind compression and rebound adjusters out until they hit their stops.
2. Gently but firmly clamp the two flats on the shock body (where the shaft comes out) in the vice. Use something between shock+vice to avoid damage.
3. Grab the piggyback resovoir in with your hands, and turn it anti-clockwise (ie unscrew it from shock body)... use a plastic sheet or towel over it if you're worried. I was, but nothing came out of mine. No explosions or cool stuff like that, sadly.
4. Empty remaining shock oil into a container.
5. Get some good ATF. I had a fresh bottle of castrol atf, I flushed out the old oil really well with that. Pump the piston with your hand slowly with some ATF in there, don't squirt yourself in the eye, etc etc.
6. Empty the fluid out again. Move the piston right down to the bottom, and fill the shock to the brim with ATF. Why ATF? well, it's what I had handy - but it's quite an advanced fluid that is resistant to quite high temperatures, is roughly the same viscosity as the stock shock oil, and well - it worked, so take that!
7. Bleed. Gently pump the piston up and down, to encourage air bubbles to come to the surface. Leave it for 10 minutes, do something else, then pump again, leave, etc etc. Do it a few times.
8. With the fluid full to the brim, fill the cap up a little as well, and basically you want to try and close it up with as much fluid in there as possible.
9. Rub some silicone oil/grease on the shaft if you want to be pedantic, then clean it well, install everything nicely, and try it out. The rebound adjustment should work perfectly, the shock should function silky smooth, and you'll want to wind the compression knob all the way in to make the best use of the nitrogen left in the resovoir.
10. Decide that mums vegetable oil wasn't a good enough substitute for ATF and tell yourself you'll use the right fluid next time.
Ah yeah, before anyone abuses me, read the disclaimer, yes I went through this process carefully and it worked perfectly for me - if anyone wants more details feel free to PM, or im happy to post as long as it won't upset industry people bla bla.
-Udi
