Bladder burst....... AGAIN!

[skipn8r]

For the second time in a row, I've reassembled my shock after revalving, and everything seemed OK......... until I open the shock after a ride to discover I've burst the bladder (pretty messy if you've never done it). Judging by the location of the hole in each case, I'd say it seems the bladders each expanded into the recess that feeds the compression adjuster. This seems to mean that I haven't debubbled sufficiently, leaving a large air void that the bladder over-expands to fill (???). That being said, I don't see how I could debubble any better than I did, especially last time.

Topped off and pumped several times until bubbles didn't appear when pumped, installed compression adjuster, pumped several times, removed compression adjuster (tilted to keep oil in both chambers), topped off again, filled bladder with 7 psi air (a few bubbles came out), topped off while air was released from the bladder (no air got into either section of the shock), topped off, reinstalled compression adjuster, pumped many times, left over night vertically, pumped several times, removed compression adjuster, pumped and topped several times with no bubbles, put 7 psi air in bladder, no bubbles, topped off, dipped compression adjuster in oil, installed compression adjuster, released air, pressurized 142 psi with Nitrogen.

After closing the shock and before Nitrogen, I couldn't hear any air "leakage" sounds when the shock was compressed and extended.......... Everything seemed good, quiet and smooth.

I'm using OEM bladders, Maximum fork oil (5 wt), and known good nitrogen at 142 psi. The inside of the bladder tube looks good, no obvious damage anywhere. I verified the Nitrogen pressure by measuring the force (28 lbs) on the shaft after rebuild.

Am I just inept??

[HairyScary]

That kind of sucks, doesn't it? I seem to recall reading that RaceTech (or some suspension shop, anyway) did the precharge to about 40psi of air (versus the shop manuals 7psi), so the bladder should be able to take a bit of abuse even with no oil around it to counter the expansion. It sounds like you were pretty thorough when doing the bleeding, although it is hard to convey with words vs. watching over your shoulder.

After bleeding as much as possible with slow strokes with the shock in the vice (wooden v-blocks around the body) I tried to do a few faster strokes with the compression adjuster in and a rod thru the lower clevis so that I could put my feet on it and push/pull on the body. Hopefully this at least unseats the shims so that no air sits trapped in the valve. On the showa xr400, the free bleed is right up there in the middle of the piston, but on the KYB, the free bleed is further down the shaft, so on that one you really can get air trapped under there if you only do slow strokes that just push oil thru the free bleed path (thru the centre shaft). I suspect that the faster strokes can emulsify any remaining air into the oil, so some standing time between doing this can't hurt by letting it separate out to the top where you can then get rid of it.

The other option, if you are convinced that you have not bled it properly by using the service manuals method, would be to fill/bleed it at the seal head which seems to be what all the suspension shops do (because it is probably quicker for them, at least that is my guess.) You have to drill the seal head below the o-ring if it doesn't have a bleed hole there already - I can't remember if it does. Do a google for Showa_shock.pdf or KYB_shock.pdf - they describe shock rebuilding and this style of bleeding (I think).

Keep us posted as to how you make out.

?

[skipn8r]

Thanks Hairy. The best I can tell is that I just did not bleed sufficiently. So, I got creative. I decided that a submerssion technique was in order. I got some 1" vinyl tubing to fit in the adjuster hole with the adjuster removed. The adjuster hole has a recess that is about 1.055" ID. So, I wrapped the vinyl tubing with enough teflon tape to take up the extra space.

Shim stack note, becuase my current stack has fewer overall shims than the factory stack, I calculated the thickness of both the factory compression and rebound stacks and added enough 21 x 0.3 shims to make sure my stacks were equal to original. This ensures that the piston is where it should be on the damper rod.

At first, I started with the compression adjuster installed. Since I had the shock completely apart, I filled the bladder space with oil (Maxima 5wt) and installed the bladder (with Schrader installed to avoid collapsing). I then filled the reservoir with oil and installed the damping rod slowly (I soaked the assembled damper rod in oil for about 30 minutes before installation). I pressurized the bladder just enough to seat both plates against the clip rings and released the pressure. I then laid the shock down with the compression adjuster up and removed the adjuster. I then inserted the vinyl tubing in the adjuster hole - the fit wasn't excellent, but it managed to hold back the oil for some time. I then added enough oil to the vinyl tube to raise it's level about 2 inches above the shock. Then I put the shock in the vise at about 45 degrees with adjuster hole up. With the help of my (patient and kind) wife, I got an opportunity to run the shock through it's stroke and monitor the bubbles coming out without danger of sucking air into any part of the shock. I then pressurized the bladder to 7 psi (no bubbles) and repeated everything many times. All the time, I had the entire compression adjuster soaking in an oil bath. After I had completely no more bubbles, I laid the shock horizontal (adjuster hole up), removed the tubing and immediately pulled the adjuster out of the oil and installed it. I forgot to take pictures during the effort, but here is a mock-up photo after the fact. So far, I'd have to highly recommend this debubbling technique.

As for the shim stack, I am assuming that I have not had a good debubbling all along and any previous stack results are suspect. I have decided to closely duplicate HairyScary's rebound stack (with a few extra high speed shims). I've come up with my own compression stack. My worksheet for today can be found here.

BTW, the knee injury turned out to be a ruptured ACL - not so good. Actually, I think it's an old Tae Kwon Do injury that wasn't correctly diagnosed. I'll find out about surgery November 9. (Note to self: when I put out my leg to stop a front end wash-out, point knee and foot forward and bend knee.) Oh well. I'll post stack results as soon as I have them. Thanks again to both HairyScary and Kelstr ?.

[cmilktm]

You are making this way too hard.

Buy a race tech video and call it a day!

Assemble the shock minus the bladder installation and the shaft installation.

Fill the bladder a 1/3 of the way up and fill the shock boddy the same amount.

Then install the bladder and preasurize o about 20psi with air.

Watch the oil level go up in the shock body.

Insert the shock shaft and fill the body up to about an inch from full.

Pump the shock shaft untill no more airbubbles apear.

Becareful not to pull the shaft out to far so that the bleed hole in the shaft draws air.

After no more air bubbles try inserting the shaft seal head .

If you hae the right amount of oil you will need to release the air in the bladder while you push the seal head down to get in in place.

Install the clip, put the cover on and put about 50psi in the shock.

The shaft should extend out to max.

depress it to check for bubbles or lack of oil.

If it is consitent presurize bladder to 150psi and call it a day.

Too easy!

goodluck

[skipn8r]

I'm probably making it too hard becuase I've grenaded two new OEM bladders (after one easy ride each) after following Honda the manual step by step. To be honest, what you've outlined is really close what I decided to do last night, just with the addition of the vinyl tube. Seems to me that the vinyl tube is a good way to ensure that you CAN'T draw air into the shock while debubbling. At $1.50, it's cheap compared to $20 for a new bladder.

BTW, if you know of anything that will cause a bladder to go (other than bad debubbling), I'm all ears.

[cmilktm]

I do not think you are sucking air in.

I think you never got rid of all the air in the first place, or you do not have enough oil in the bladder area.

Leave the asjuster installed and only do all your work and bleeding from the shock housing.

Doing it by the manual is a nightmare.

Just make sure you have the adjuster adjusted softer out so that oil passes easier.

doing it by the manual procedure is a nightmare and will just cause you more grief than anything..

[Woody_393]

I do not think you are sucking air in.

I think you never got rid of all the air in the first place, or you do not have enough oil in the bladder area.

Leave the asjuster installed and only do all your work and bleeding from the shock housing.

Doing it by the manual is a nightmare.

Just make sure you have the adjuster adjusted softer out so that oil passes easier.

doing it by the manual procedure is a nightmare and will just cause you more grief than anything..

I agree. I just did mine last night using the exact procedure and it was cake to bleed the air out with the process he just outlined (I used this source --> http://www.motocross.com/motoprof/moto/mcycle/shock/shock.html and it worked great.