Specialized FSX Future Shock Fork /RS Mag 21 Service

[FluffyChicken]

What air pressure are you putting in it.
Other than the ports blocking/lockings
or the circlip snapping and still in the bottom
Or the o-ring are locking it up.
But that's not something I've seen happen.

 

[.RJ]

35-40psi air pressure, oil level 40mm from the top with the fork legs compressed.

 

[FluffyChicken]

Pump them up to 100PSI (you're suppose to do that after a service and leave for a while to let stuff settle, but that's not the point here).

And see how they work at 100PSI or there abouts.

 

[.RJ]

Why 100psi? The max pressure I can find for any of the rockshox or FSX/Future shock service manuals is still under 50psi so 100psi would effectively lock the fork out.

I blew apart the fork legs again yesterday to see if perhaps I'd missed something and I dont think so - as I was filling the fork up with oil and cycling it, it seemed that the closer I got to a full oil level, the more likely it was to bind up and stick at the bottom of its travel. So it sort of feels like a hydraulic lock, but, it could also be binding. One of the fork legs took a significant amount more pressure from the floor pump to separate the lowers and the same fork leg required some persuasion to seat the bushings into the lowers. Once in, it moved really nice though, so I wonder if with the fork brace and wheel on something is causing that leg to bind.

With no history and obviously someone in there before adding o-rings that didnt belong (and it was very low on oil) who knows what happened to it in the past.

 

[FluffyChicken]

100PSI just make make a really stiff spring for the rebound to see if it does come back up during use.

 

[Patto]

Im thinking you may have to tackle one part at a time! the forks cycle through with out the wheel in? i would try with out the brace and wheel in as they may have been damaged at some stage and have twisted and hence bind. At least you will have more of an idea

 

[baldric 75]

I'm currently stripping/servicing a pair of these and mine were staying down after full compression too. When I blew the left leg to separate the stanchion and slider that fat 'O' ring was right in the bottom of the carbon slider on what looks like a white nylon bung blanking off the tapered bottom section of the slider which would suggest yours may have been wrongly rebuilt before you had ahold of them?
The set I've got are from a 94 Stumpjumper FSR and the chap was the original owner and never layed a spanner on the bike in 29 years

 

[FluffyChicken]

Memory serves ('92 MAG20 which the construction is styled on, (not the 93+ MAG21s).
In the leg there is the white 'plate' has big oring above it that you can see.
Creates a buffer (bottom out).
The mid-fat o-ring on the stanchion at the bottom is also a buffer (top-out).

 

[.RJ]

@FluffyChicken - I see the white plate at the bottom of the lowers, but there's no o-ring down there - there was originally a big fat o-ring that was shoved under the plate that the fork seal sits on but the circlip wouldnt engage with it there and I couldnt find any other reference to this in any of the manuals. Should that be hanging out at the bottom of the lower?

So I've been ignoring this project for a while with some dead ends locally looking for some help - so I'm diving back in. I found a set of NOS fork bushings that I'm going to swap in as the ones I have do show some wear but seemed tight with no play - i cant think of anything that would cause the sticking at the bottom of the travel.

The kit also included these little short springs - is this something the fork should have in it? I've seen some videos and DIY guides that show these at the bottom of the fork lowers - they dont seem very stiff, are they meant to assist in fork bottoming? Should I have them? Turn them into christmas ornaments?

 

[FluffyChicken]

They're MAG21 bushings, seals etc. The springs are negative springs and not in your forks.

Hopefully the bushings are the correct ones as that FZX is sort of a bit of both MAG20 and MAG21.
Just measure the outer diameter to make sure. (or compare them).

I'll have to have a reread and maybe dig out some forks. I don't have any FSX forks to hand though.