Shock Rebuild Help

CSAR FE
Posts
645
Joined
5/30/2017
Location
Tucson, AZ, USA
Having some issues with my shock. It was revalved previously by FC, and had a bladder kit installed. I was very happy with the performance. I decided to service it when I swapped my AER forks out for my Ohlins forks. Here’s what I did:

- Rebuilt Seal Head
- Installed new piston
- Installed new bumper
- Hand-bled shock using normal method, without vacuum bleeder, until no bubbles present. Used KYB K2C oil (same weight as FC’s shock fluid)
- Filled Bladder to 140 PSI with nitrogen

I used all WP parts. The shock has felt very soft and the rebound has been a bit too fast since I serviced it (so far it has not bottomed out, incidentally). I have pulled the shock back apart to verify the piston was oriented correctly, and rebled it three separate times now. I know for sure the correct shim stacks are on the correct sides of the piston. I also verified that the rebound rod was moving in the shaft when moving the adjuster. Additionally, when I originally installed the new piston, I did not surface it like the WP manual calls for. I did that on a piece of glass this last time around and felt no change. I verified my clicker settings. I’m at a loss at this point, and am starting to wonder if this whole thing is in my head. Any ideas?
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TC125
Posts
23
Joined
5/8/2020
Location
CA
7/16/2020 2:58pm
Sounds like you have done everything correctly to me. I don't use the vacuum bleeder either and haven't had any issues, done it three times this season and my oil has came out looking like new every time. Is the new piston the same as the old one as in diameter/ports? Wonder if it's bypassing due to a slightly smaller piston? Was also wondering if the different forks were affecting the rear end but would think that would be more on the compression side. Maybe give a different oil a try and see how it works?
CSAR FE
Posts
645
Joined
5/30/2017
Location
Tucson, AZ, USA
7/16/2020 3:22pm
TC125 wrote:
Sounds like you have done everything correctly to me. I don't use the vacuum bleeder either and haven't had any issues, done it three times this...
Sounds like you have done everything correctly to me. I don't use the vacuum bleeder either and haven't had any issues, done it three times this season and my oil has came out looking like new every time. Is the new piston the same as the old one as in diameter/ports? Wonder if it's bypassing due to a slightly smaller piston? Was also wondering if the different forks were affecting the rear end but would think that would be more on the compression side. Maybe give a different oil a try and see how it works?
The forks affecting the shock crossed my mind as well. I’m sure that’s entirely possible.

The piston fits tightly into the shock body. It looks exactly the same as the original, and the original didn’t look like the ports were altered by FC. I don’t think it’s bypassing. But of course, a fraction of a millimeter could make a difference I’m sure.
7/17/2020 1:49pm Edited Date/Time 7/17/2020 1:56pm
What was previous oil in shock? As in cst, recently I rebuilt my ktm shock and went with k2c oil, I noticed the same thing it felt softer, I just turned In compression a few clicks, I dont know what the fc oil is compared to kyb or motorex oil, but might have less viscosity so it essentially might be lighter in that regards.
CSAR FE
Posts
645
Joined
5/30/2017
Location
Tucson, AZ, USA
7/17/2020 2:11pm Edited Date/Time 7/17/2020 2:14pm
What was previous oil in shock? As in cst, recently I rebuilt my ktm shock and went with k2c oil, I noticed the same thing it...
What was previous oil in shock? As in cst, recently I rebuilt my ktm shock and went with k2c oil, I noticed the same thing it felt softer, I just turned In compression a few clicks, I dont know what the fc oil is compared to kyb or motorex oil, but might have less viscosity so it essentially might be lighter in that regards.
Previous oil was presumably FC’s, as they revalved it last time the shock was open. I couldn’t find the cst for the FC oil when I was getting everything together to service my shock and the KYB oil was the same weight but cheaper, so it went that route. The oil very well could be the case. At any rate, I sent the shock to FC today, to let them figure it out.

The Shop

7/17/2020 3:20pm
I called them, they did not know the cst off hand, said they would get back to me, I'm curious if maybe the kyb oil is a little lighter.
1
TC125
Posts
23
Joined
5/8/2020
Location
CA
7/17/2020 4:50pm
It would be interesting to know if that's the difference - would make sense
7/17/2020 5:15pm
FC used to use Maxima oils. I’m not sure if they still do though.

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