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Discussion Starter · #1 · (Edited)
So I am in the middle of a rebuild of a broken down 1991 EXT Special.

At this point, I am tackling the Fox shocks. (I believe these were known as the Fox "Gold" shocks due to the stock body color)

The 2 rear (track) shocks are a mess; corroded bodies, rust all over the shafts, and little pressure left. (see pic)

I need to dismantle these to see what I need to replace.

Here is a good site (uses Kings, not Fox) which explains how these shocks work.

http://www.off-roadweb.com/tech/0906or_off_road_race_shocks_explained/

And here is a good video of a newer model (and much better condition) shock rebuild, although the principles are similar.

https://www.youtube.com/watch?v=POunLnsInQk
 

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Discussion Starter · #2 ·
First step is to bleed out the remaining pressure. In my case, there is almost nothing left. For a decent shock, use caution when bleeding, as they take 200 psi of nitrogen.
 

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Discussion Starter · #3 · (Edited)
The rear track shock is the larger of the pair, and has the reservoir attached via a hose.

To drain the oil, I removed the metal band clamping the bodies together and disconnected the reservoir hose from the main shock body (7/16 wrench). I was able to drain most of the oil that way.

(That oil smelled REAL bad !)
 

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Discussion Starter · #4 · (Edited)
Next task was to remove the shock cap.

This takes a 1-inch wrench, and was so firmly on there (including loctite, it seems), that ultimately I had to resort to heating the body with a propane torch.

Heating to loosen the cap threads was straightforward for the rear shock, which already had most of the oil drained.

However, I was not able to drain the oil from the front shock in the same way, and so the oil was in there while I heated the body. So, prior to heating, I made good and sure that the nitrogen reservoir was thoroughly bled.

Once I got it loosened, I placed the shock outside in the firigid February air to cool, before removing the cap completely.
 

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Discussion Starter · #6 · (Edited)
Here is a closeup of the piston.

You can see the piston with its oil ports, and the bumper on the bottom of the cap.

Too bad the exposed portions of the shafts are a mess; the insides of these shocks seem to be in pretty good shape.
 

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Discussion Starter · #7 · (Edited)
Next steps are:

- get replacements shafts
- get rebuild kits for the O-rings, wipers, etc etc
- clean and paint the exterior of the shock and reservoir bodies (I'm going to do Grabber Green -- I mean, "Arctic Cat" Green
)
- a local Arctic Cat dealer will fill the shocks with nitrogen for a nominal fee

I will post follow ups as I get the above done.
 

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Discussion Starter · #8 ·
Cap Seal Replacement - 1 of 3

Here is an example of replacing the cap seals (2 nylon scrapers, and a small O-Ring)

Here is the cap after all the old seals were pulled out. There are 3 grooves that each of those have to go in. In fact the larger of the 2 nylon scrapers goes in the middle of the cap.
 

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Discussion Starter · #9 ·
Cap Seal Replacement - 2 of 3

SInce you have to pretty much stick the seals in the shaft hole almost sideways and work them into their grooves, I used the flat end of a large drill bit as a face to press the seals against, so they would seat into the right groove and not just pop out the other side.

The good thing is, once you get them worked in a bit, they tend to pop into place nicely.
 

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Discussion Starter · #11 ·
I am currently waiting for the oil to come in (Amsoil Shock Therapy #5).

The new shafts are in, and the bodies are cleaned and primed, so I am on the home stretch.
 

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Discussion Starter · #13 ·
We fashioned a "piston puller" out of a long threaded bolt (1/4-20 x 7 inches) and a wooden dowel (see attached). This screws right into the threaded hole on the internal floating piston, so we can pull out the IFP, as well as position it to depth.
 

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Discussion Starter · #14 ·
The attached shows the new shaft attached to the main body piston. Blue Loctite on the threads holding the shaft end nut on, red Loctite for the threads holding the eye bolt at the other end.
 

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Discussion Starter · #15 · (Edited)
Filling the shock with fresh oil

Note that on these shocks, there is no bleed hole on the internal floating piston, so getting any air pockets out is an art.

Here is how we added the oil and got the air out:

1. Positioned the internal floating piston all the way in.

2. Poured oil in the main shock body, about half full or more.

3. Pulled the IFP back up, sucking some oil through into the reservoir.

4. Sealed the open end of the main shock body with Saran Wrap + rubber band, and turned the shock upside down.

5. Carefully pushed the IFP back up (deeper into the reservoir) pushing the air through to the other side -- need to be careful here, so as not to pop the saran wrap ! The trick is to put the saran wrap on loosely. (Next time, I am going to do it before the above step 3.)


The theory here is that by turning things upside down, any air pocket in the reservoir rises to the "top" -- which is now the bottom where the chambers connect (via the flexible hose in the rear track piston; via the solid chuck in the front track piston) -- and so by pushing the IFP we can push the air through to the main reservoir.


6. Turned things right side up, in theory making the air now rise up to the top of the main reservoir (still open at this point)

7. Added oil, and positioned the reservoir IFP to the right depth (2.30 inches for both of these)

8. Inserted the main shaft and piston. The oil flows through the holes in that piston, so it is possible to submerge it entirely.

9. Once the main piston was submerged, filled the main body, up to 1/4 inch from the top.

10. Carefully screwed the head on with a crescent wrench, wiping oil spillage with a towel.

Once we tightened the end cap, we tested the shock for air bubbles. We did this by securing the bottom (in a vise, in our case), pushing the shock shaft all the way down, then pulling it up as fast as we could.

On one of them, we heard a chirp at the end, which is a sign that there is still air in there. Apparently it is possible for air to get trapped in between the various plates, piston ports, etc on the main shaft. The technique we learned to solve this was to use a rubber mallet to rap the eyebolt smartly, with the end cap still screwed on, to "shock" the bubbles out. It turned out to take some good whacks to do so -- for example, in a serious of quick whacks I knocked the shock from full extended to all the way in. Testing it this time revealed a much different chirp, which suggested we got the air up to the top, just under the end cap.

Sure enough, after taking off the end cap, carefully topping off the oil (make sure the main body piston remains fully submerged), and then re-securing the cap, testing revealed that there was no more "chirp", and so we had a good refill.

Nitrogen is up to 200 psi, although I understand that some folks say to exceed that (probably due to the fact that the Shrader valve has a spring that exerts a certain amount of force)

We had the nitrogen refill done by a friend, but I previously had discovered that the local Arctic Cat dealer would do nitrogen refills for $10 a shock.
 

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