KYB SSS won’t rebound fully

hubbardmx50
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hubbardmx50
I’m not sure if this is something that’s been covered already but I’m working on a set of forks off of a 2012 Yz125 and after bleeding and seeing no bubbles and installing the shim stack valve back into the inner cartridge the damper rod won’t rebound fully on its own. I’m using the recommenced oil amount 7oz and bleeding exactly how the manual says and not fully extending the rod each time. This is super frustrating as my buddy drove an hour to have me get these done tonight and I can’t seem to figure out why it won’t rebound. Any help is appreciated thanks
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jaredkeller96
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jaredkeller96 6/4/2020 9:42pm
6/4/2020 9:42pm
hubbardmx50 wrote:
I’m not sure if this is something that’s been covered already but I’m working on a set of forks off of a 2012 Yz125 and after...
I’m not sure if this is something that’s been covered already but I’m working on a set of forks off of a 2012 Yz125 and after bleeding and seeing no bubbles and installing the shim stack valve back into the inner cartridge the damper rod won’t rebound fully on its own. I’m using the recommenced oil amount 7oz and bleeding exactly how the manual says and not fully extending the rod each time. This is super frustrating as my buddy drove an hour to have me get these done tonight and I can’t seem to figure out why it won’t rebound. Any help is appreciated thanks
Could be a free piston seal.
FWYT
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FWYT 6/5/2020 8:42am
6/5/2020 8:42am
jaredkeller96 wrote:
Could be a free piston seal.
Thought that, too.

Also what has worked for me, and I'm probably doing something wrong along the way that I need to do this in the first place, but once I bleed the cartridge, I set it aside for an hour or so before I put the compression adjuster assembly. Just to give any tiny air bubbles a chance to float to the top.
hubbardmx50
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hubbardmx50 6/5/2020 1:22pm
6/5/2020 1:22pm Edited Date/Time 6/5/2020 1:30pm
Another thing I’ll mention is that I’m doing both forks and the other fork had the same issue but after about an hour I did eventually get it to extend fully on its own. I’m not sure what I magically did any differently.....

Just tried working on it again and got very close but there’s still about 2-4 inches that won’t extend on its own. Again I’m measuring the correct amount of oil, bleeding according to the manual (says don’t extend past 8 inches) and I see no bubbles. By visually inspecting the base valve I don’t see any cracks or torn up O-Rings. Any more suggestions? Thanks
ctb108
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ctb108 6/5/2020 2:07pm
6/5/2020 2:07pm
Is it possible that it wasn't rebounding before you rebuilt?

I have not done this on SSS forks so I am not sure if it's the same.... but on a set of Showa RM 250 forks I had the same problem. Changing the inner cartridge seal fixed the problem. I am sure there will be a youtube video and is probably mentioned in your service manual.
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FGR01
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FGR01 6/5/2020 3:03pm
6/5/2020 3:03pm
Most likely you're not putting enough oil in before inserting the compression assembly. This results in a "sucked down" condition when you bleed it.

Instead of putting a measured amount of oil in, just fill it up until the noticeable step shoulder is covered with about 10mm of oil. Bleed it properly, then add oil again to bring the level back to about 10mm over that shoulder. Stroke it some more to make sure all air is out.

Essentially, you can't overfill it because any excess is going to be forced out when you insert the compression assembly and then stroke it a few times. Just make sure you get rid of this excess by blowing it out the weep holes.
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hubbardmx50
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hubbardmx50 6/5/2020 6:06pm
6/5/2020 6:06pm
FGR01 wrote:
Most likely you're not putting enough oil in before inserting the compression assembly. This results in a "sucked down" condition when you bleed it. Instead of...
Most likely you're not putting enough oil in before inserting the compression assembly. This results in a "sucked down" condition when you bleed it.

Instead of putting a measured amount of oil in, just fill it up until the noticeable step shoulder is covered with about 10mm of oil. Bleed it properly, then add oil again to bring the level back to about 10mm over that shoulder. Stroke it some more to make sure all air is out.

Essentially, you can't overfill it because any excess is going to be forced out when you insert the compression assembly and then stroke it a few times. Just make sure you get rid of this excess by blowing it out the weep holes.
That’s correct, I always overfill just a tad because the excess comes out anyways. Cool yeah that would make sense, I’ll give that a try.
hubbardmx50
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hubbardmx50 6/5/2020 6:09pm
6/5/2020 6:09pm
ctb108 wrote:
Is it possible that it wasn't rebounding before you rebuilt? I have not done this on SSS forks so I am not sure if it's the...
Is it possible that it wasn't rebounding before you rebuilt?

I have not done this on SSS forks so I am not sure if it's the same.... but on a set of Showa RM 250 forks I had the same problem. Changing the inner cartridge seal fixed the problem. I am sure there will be a youtube video and is probably mentioned in your service manual.
It’s not my bike so I’m not sure. He wasn’t complaining of any issues we just tore it apart because the seal was leaking. Surprisingly there’s not any good SSS rebuild videos on YouTube. Rocky Mountain has an awesome in depth video for the Showa 49mm forks which is what my bike has and a lot of other forks but nothing for SSS surprisingly.....
rollin64caddy 6/6/2020 4:08pm
6/6/2020 4:08pm
I started a thread about the same thing with my showa forks. I couldnt get it to rebound all the way either. I took it to my suspension guy and he recommended turning the compression valve as you slide it into its chamber to allow the oil to get all the air out. Can't remember if the kybs are the same but maybe give it a try. Good luck.
bh
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bh 6/7/2020 3:18pm
6/7/2020 3:18pm
Cartridge and/or free piston seals.
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hubbardmx50
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hubbardmx50 6/12/2020 5:32pm
6/12/2020 5:32pm
Tried it again a couple times this week, oil measured and bled perfectly before installing base valve with no luck. I can't even get it to come out enough to put the rest of the fork back together if I wanted to. Where should I tell him to send it to have it looked at? We're in Socal so we have a lot of options. I was thinking RaceTech since they're close and probably stock the parts for this valve that can't be bought off the OEM diagram from a local dealer.
Nial_Darragh 6/13/2020 2:56pm
6/13/2020 2:56pm
There isn’t enough spring pressure at free pistons it’s perfectly normal for the rod not to fully extend on the older sss

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