Rock Shox Mag 21 style air needle valve

[FluffyChicken]

I can post at last, not just read PM's and posts.

They are standard (later) seals. Seen them in 95+ topcaps, Ignore the flap unless there is no adjuster rod for it to sit on.
I have some 'flap' and non-flap sat waiting for me to use. Mine are a stiffer compound than the original (I have as few pairs of originals as well)
My stiffer work better. If you can get optics pins then these work well (a large pin really) to make the hole. Getting it straight I always find the hardest on mine. Not so much of a problem on the pre '94 ones but the 94+ need it central so the needle sits in the adjuster rod. The little bit missing I found helps reduce end tear. I just cut mine in.
You need to make the hole on the originals yourself as well.

In reality your method will work but you may as well just stick it into the adjuster I would have thought?
I intend to try this on the more troublesome mag30 which use a slightly different method and its the container that leaks.

Mine are tried and tested and in use by a few. I usually fit them myself, test and pressure test with soapy water etc. But that usually a full build and it fun to make your own.
Don't make money from them especially considering the time involved, but it's nice to get them running.

They are 8mm diameter by the way. The flaps make them a little longer than the standard but it locks them in place.

 

[FSXStumpy]

Thanks, fluffy, I'll get'er done! Seems a fun project to me.

Now I just gotta find a pair of Mag 21's for my wife's Hardrock AX, and I'll be set. Between Enduro seals and homemade needle valves, there's not alot left to go wrong on these old air-oil units, which I've always enjoyed riding and tuning.

J

 

[FluffyChicken]

I've seen an o-ring destroy itself. Pair of mag20's. One of the valve ones went, I think.. Could have been a lower bushing size one and jammed itself through the valve holes, all of them.

The circlips snap of the end. Bushing tend to last, which is lucky
Biggest problem with them is cracking around the lower leg bolt holes.

What length steerer do you need for the wife's bike?

 

[FSXStumpy]

Well, back from a week's vacation, with success to report!

First, FluffyChicken, I've seen O-ring problems with my fork in the past too: Mine has long been hard on the O-rings that are installed above and below the bushings. After a season or 2, these rings tend to need to be replaced. The symptoms of their failure are hydraulic-locking of the fork after a big hit. The fork simply fails to rebound until it's re-compressed, then it usually comes back. $2 of new orings and an hour's work sorts it each time.

Back to the needle valves:

I had moulding problems with my first attempt at moulding the needle valves with the hole partially pre-cast. It made getting a good mould fill difficult and the wax slowed the curing down to glacial rates. Only 1 of the 4 pieces i moulded was good enough to want to use. I tried it, and it worked!

I'll describe exactly what I did, so the next guy might find the info easily:

I made a maple mould with four 8mm holes drilled thru it. The wood was about 3/4" thick. I drilled slowly to produce as smooth sided holes as I could.

I chose Permatex Ultra Black RTV sealant, on the basis of its claimed resistance to oils.

I used a toothpick to smear a thin coating of vaseline inside the wooden mould. I removed the tip from the RTV tube, and carefully filled each mould chamber, from the bottom up, ensuring no air bubbles were included. I covered the ends of the mould with strips of newspaper, and set the mould aside for 3 days.

When it came time to eject the plugs from the mould, I chucked a deck screw into my bench vice. Happily, its head diameter matches the holes well. The plugs pressed out with easy force. Squeezing each plug between fingers would reveal its quality, air holes showing as soft spots. I only needed about 10mm of each plug for my valves (the originals are 10mm long), so I chose the best segment of each valve, and trimmed the ends with a razor sharp knife.

Now I needed to puncture the needle hole thru each valve, and I chose to do this before installing them in my fork. I took a 15ga spoke, and cut off the head. I chucked it in my drill, and spun it against the side of my bench grinder's wheel until an acute point was formed. I had noted that the original needle valves used a 3-sided puncture, so I refined the point to a triangular one on a whet stone. Finally, I pushed the needle thru the middle of each valve piece. It went thru easily and cut a nice 3-sided pattern, smaller but not unlike the original valves.

Inserting the new valve in the fork air caps was easy enough, just poke'em in. They're retained by the adjuster rod tops upon assembly.

Once assembled, I lubed the tip of my inflator needle with grease, inserted it and easily inflated each leg to the 44 pounds I prefer to ride it at in these, my heavier years. Each valve sealed quickly and surely upon needle removal.

Thanks for the tips, guys, you were spot on!

FluffyChicken, I need about a 180mm steerer for the wife's bike. She just made the jump to clipless peddles this past week, however, so the bike budget is shot for a couple months.... LOL.

J

 

[FluffyChicken]

When rebuilding the fork, probably not needed for the valves alone. Pop the pressure to 100psi and leave for a while.

I test my valves at 100psi plus.

But the pressure is to get everything to sit into place, as per service instructions.
There was, as far as I know and I have one, a black tubed much easier to use pump for servicing, goes to 100psi+
The adjusting one is a medical syringe and goes to 60psi but has easier accuracy around the 35-45 range

 

[FSXStumpy]

Yes, correct, seat the seals with 100psi per leg for 24 hours says the book.... I used my frame pump to do the job. Easy enough. Didn't wait the 24 hours, though, just pressurized to about 120psi, relieved back down to 45 and rode'em. Pressure hadn't changed upon my return.

Some people seem to think that such pressures will damage the fork, but they forget how they work! It may be 45psi at full extension, but compressed, the fork's under about 150-200psi. The oil pressure during fast compression can be much higher still.

I still use the old syringe pump for normal work, but not for blowin' the forks apart or for initial seating of seals. When I worked in a shop, we used to use a better shock pump, about a foot long, black alu unit, I think it was a Fox offering. But the Rock Shox pump works OK, especially once you figure out how to make syringe rubbers work properly on'em.

So happy to have my forks back to easy-pressure-setting bliss!

J

 

[dencal]

Re:

Dear all,

i'm in trouble with my Rock shox MAG10 ,because the air valve.

you think this "silicone" cord with 8,4mm diametrer ,cutted to 10mm lenght will be ok instead to self made it ?

Thanks a lot to help me on this.

http://www.ebay.it/itm/Metric-Black-Rub ... 1895290528

 

[FSXStumpy]

It might well work... However, I don't see anything that says that is silicone cord, but nitrile rubber. I would expect this typical O-ring material to be too hard. Diameter seems appropriate, just needs to be soft enough.

The method for moulding your own as described in this post does work well and easily too. The last set I made are now in service 2+ years with no trouble.

J

 

[dencal]

Thanks a lot for your quick reply FSXStumpy !

You know maybe , the best way/tool for pierce the new valve on the center ? Medical syringe or different tool ?

Thanks !

 

[FSXStumpy]

Ideally, you want to pierce with something that will leave a decent hole for the air needle in the future. I sharpened a spare spoke to a 3-sided point - Worked well.

A large, sharp sewing needle may also work.

J