Anyone consider the possibility that the pressures might be comming from the type of fluid there running . ( specially those who are saying there not into their bottoming cone ). Another thing I have noticed is worn fork seals even though they are not leaking but will allow air in on the reb stroke.

Adammoto, on 09 March 2012 - 08:22 AM, said:

Thanks alot
Meassured the seal and its 4.2mm high at the edges and maybe 3,7-3,8 at the inner edge so i made my depth 4,0mm so that the metalring above the seal would hold it in place.
Maybe i should  copy yamaha227:s idea and machine the sealholders inner edge and make a new sleeve that holds 2 seals




seal head mod dual seals wp tc by henso72, on Flickr

Edited by henrics, 09 March 2012 - 02:26 PM.

russ17, on 09 March 2012 - 01:49 PM, said:

No Haven't considered the fluid type as an issue, i use motorex 5w. I would have thought if it was the fluid causing it, shouldnt the baldder pressure drop back tot he original set pressure once the fluid cools?

I have done the mod to the seal holder on one fork to accept another seal facing the other way. Installed an older type seal holder and seal on the other fork so i can compare bladder pressures between the 2 after some decent rides, had a big 2 day enduro on the weekend which included a final moto.... with plenty of holy shit bottoming moments, haven't had a chance to recheck pressures yet, but should be able to report tomorrow.
But overall, forks went good... DFMV is working good adam

How about using a showa cart seal. on the new sealholders one must mod it or make a thin sleeve. but on the old the job isn`t more than the one i made for the skf seal.

borrowed the pic from kan3 here on tt

henrics, on 11 March 2012 - 05:16 PM, said:

Is the showa seal less drag than the older type wp cart seal? That is the big bonus of the new wp skf purple cart seal, so much less drag than the older seal type.... but maybe its coming at a cost....

yamaha227, on 11 March 2012 - 04:25 PM, said:

Good to hear Ben.  I have the modified seal holders ready to go - just need to test them.

Just checked my bladder pressure after 10 hours of enduro on the weekend.

Extra purple skf seal facing the other way doesn't work.

L/H fork bladder pressure with 2 skf seals checked at 26 psi.

R/H fork bladder pressure with older type seal (different to oem though) supplied by dave checked at 10 psi. Allowing for escaping air to fill short line and gauge, 10 psi sounds about right with initial set pressure of 16 psi.

Last bleed method i tried was WP method explained in pdf doc on mx-tech website. So my original bleed method was fine as nothing has changed with increasing bladder pressure being caused by excess fluid entering inner cart and not bleeding off enough.

Keen to here thoughts......

So you have your fix?daves seal

yamaha227, on 12 March 2012 - 12:06 AM, said:

Did you take a photo of the seal you used?

Good on you for trying the two skf seals, bummer it didn't work.

yamaha227, on 12 March 2012 - 12:06 AM, said:

I'm glad the new seal worked for you.

Apart from the air that fills your gauge when re-measuring, you will also notice a lower pressure because after filling the bladder to 16psi, you purge the excess oil from the cartridge.  This loss of oil will cause the bladder to expand and therefore lower the pressure slightly.

I found more proof that the cartridge purges the excess oil too slowly.  I assembled and pressurised a cartridge and begun to purge the excess oil.  I partialy compressed the rod until air/oil/ started to purge. I then alllowed the rod to extend and as it was extending, the relief valve was still letting air/oil out. So this told me that the bladder was seperating the pressure above that was purging and the pressure below that was extending the rod. This is where I reckon a machined groove down the inside of the cartridge would help purge faster.

I'm not 100% sure there is a problem, if you bottom once per lap you don't need a fast purge time, I cant believe the fill time is very fast? As long as it purges even a tiny amount each lap it should never pump up

Adammoto, on 12 March 2012 - 09:26 AM, said:

No i haven't. Dave might be able to tell us what type/brand it is. Fairly similar stiction to the older style oem seal.

dwb79, on 12 March 2012 - 02:39 PM, said:

That makes sense Dave. What sort of milling machine would be needed to machine a vertical groove in the inner cart? Looks like something along those lines could be the next option.... or stick with the older type seal.

Anyone know how a showa cart rod feals going through its seal compared to an older wp cart/seal? Ive never felt the action to compare the 2.

The showas isn't too bad for stiction apart from when the rod gets gummed up with oil deposits( a sticky residue) however the showa seal isn't exactly renound for keeping oil from entereing the inner chamber,  and the showa normally has a strong ics spring helping it, where you have a low pressure bladder

I had a chance to play with brand new WP CC fork off 2011 FE390...Once I reduced the float to 0.2 range it started to suck air even during the bleeding procedure-Once I put the oil and SLOWLY moving the rod up......It didn't stop......Later on I put more oil and put the bladder. Inflated at 30-ish psi. it was still sucking some air........The whole "suckition" process stopped around 50!!! Psi.....
Perhaps those are not intended to work with this low amount of float?! This is why the Cone Valve fork (floats around 0.2) are "supported" by ICS spring???

Where was it sucking air from? You mean during priming? Ive set them to 0.3mm and had zero problems?

mog, on 12 March 2012 - 02:49 PM, said:

But that is the problem mog, the cartridge needs to be fully compressed for longer than it would stay bottomed out on a track, before the bladder deforms enough for the oil to reach the relief valve and it starts to purge.

Of course the best approach would be to stop oil entering the cartridge, instead of trying to purge it faster, if possible.

suhoi27, on 13 March 2012 - 01:41 PM, said:

I've experienced this on low float setups with many hours on them, but never on a new one like you. I replaced the seal and it fixed the problem.

It would be interesting how long the fork stays in the bottoming cone during a full bottom,  I have no idea

These forks have been in production since 2005? In the sxs,  this is the first time I have heard of the problem, and few riders have ever commented on it,  the ones I have rode never felt like they altered in one ride,  I do run lower levels than std and the forks do bottom

Kybs etc do this when they don't bottom