so with the cartidge mananging to avoid any spoilers for me, the rebuild continues and I'm gonna copyNpaste this here, for my own ease of refenece:
To change the oil in a damper cartridge you first need to remove the aluminium cap at the end, this should just slide off if you wiggle a fingernail in the gap between it and the damper cart.. (the end to work on here is NOT the one with the circlip on)
then push the damper rod through so that the shorter length of exposed shaft is at the end with the circlip on..
the next bit is the tricky bit.. you essentially use the damper rod to push the seal out.. you either need to use a press to push the damper rod onto the rubber seal at the end or it can be done by hitting the end of the damper rod (at the circlip end) with a hammer to push the seal out.
it can take quite a bit of force sometimes!
the seal will eventually work its way out and be followed by the contents of the damper cart.. so have a container ready to catch the oil! the damper assembly will now slide out of the cartridge.. make a note of what order bits come out, as there is usually a metal washer and rubber o ring loose from the shaft
wipe clean and inspect the damper internals.. and slide the damper back in, in the same order it all came out...
the carts are filled with 5wt oil.. but you can put either 2.5wt in for less damping or 7.5wt for more..
to refill.. carefully push the damper all the way back into the cart and then gradually fill with oil.. when it gets almost full cycle the damper a few times to remove any trapped air and then fill the cart to the brim..
the next step can get a bit messy..
you now need to slide the seal back on.. but as the cart is full you need to displace some of the oil to allow the seal to fit back in..
in order to allow some of the oil to escape i put a fairly thin but strongish (maybe 1mm) square shaped rubber band in between the seal and the silver damper shaft and then slide it down.. the rubber band creates a bit of a gap to allow the oil to seep out and create space for the seal as you push it back in and means there will be no air gap.
I generally work my way around the seal pushing down with a blunt ended object to work the seal back in..
once the end of the seal is flush with the end of the damper cartridge pull the rubber band out to reseal the cartridge.. slide the aluuminium cap back on and you are done!
disclaimer: the above is a guide only and i take no responsibility if you break your damper cart!