rear shock has a sudden rebound = out of damper oil?

[SniperGaulois]

i recently bought a bike which is nearly new, except that the rear shock rebounds suddenly like a pogo stick. does that mean that it's out of oil? it's a practically undocumented shock absorber from 10-12 years ago, i don't think i can find a guide on how to service it, i have no idea what to do? too technical? i brought it to the local bike shop he said it was probably done for and that he'd never serviced a mtb shock absorber. what do they charge to service them, what should i do with it? is it difficult ot add silicone oil to a random "german-A" made shock?

 

[E-geezer]

Sounds like you've lost rebound damping, it's hard to know why. Could be out of oil if the seals are blown, or air has leaked in and now you have foam inside instead of oil. If its an old shock, it probably has simple orings for seals.

Any pics? You could probably rebuild it, you don't have much to lose anyway.

 

[Howlermonkey]

or.......it's been compressed and rebounded while upside down causing air to occupy where the valving is?

If there's an obvious leak, it's time for replacement/rebuild.

Since you will likely be removing it, get it alone and cycle it by hand (right side up) and see if damping
returns.

As a last resort before replacing it, try compressing it upside down, rotate right side up, and pull it all the way out if cycling it right side up doesn't see a return of dampning.

I was a koni, bilstein, kyb dealer and i stopped many returns because the customer pumped them upside down.

 

[Ykick]

Last winter my Fox Float rear shock suddenly stuck in full compression. I tore it apart and with a pop of air like breaking a seal it pulled apart. I studied some YouTube videos, cleaned and re-oiled the seals and it went back in service with no replacement parts. I ordered new seals but haven't needed them yet.

I dunno if this is similar to what you're facing but it was a weird one (probably due to cold temperatures) but it sure was odd the way air had leaked past and held the piston in full compression.

 

[Drunkskunk]

It could be anything, from being totaly blown, to the rebound adjustment knob or screw getting bumped slightly. I know the difference between no rebound at all and pogostick like bounce on my Marzocchi is less than 1/8th of a turn.
It would help us to know what kind of shock you have.

 

[nutnspecial]

Yes, a few pictures too if name brand and model is not evident.

 

[slackard]

Last winter my Fox Float rear shock suddenly stuck in full compression. I tore it apart and with a pop of air like breaking a seal it pulled apart. I studied some YouTube videos, cleaned and re-oiled the seals and it went back in service with no replacement parts. I ordered new seals but haven't needed them yet.

I dunno if this is similar to what you're facing but it was a weird one (probably due to cold temperatures) but it sure was odd the way air had leaked past and held the piston in full compression.

The issue that Ykick described sounds like the "stuck down" phenomenon. In an air shock, you have your main chaimber and what can sometimes happen is air burps past the main seals into the 2ndary (sometimes called negative) air chamber. Ive had a shock stick down and it literally only rebounds to about half stroke. disassembling and purging all the compressed air can remedy this situation. If the shock is stuck down, not a bad idea to replace seals when you disassemble, but may not be required if no wear is evident.

As for the OP, your shock needs service, but given its age, rebuild kits and instructions may be difficult to find, and without knowing the true issue any efforts to remedy may be futile. There are a number of online shock service companies that could help you out, but they may be pricy. If youre going to keep riding this frame, consider a new shock. Measure the shock's eye to eye length and its stroke length. Its likely a modern replacement in a matching size will bolt right in.

When my float R from 99 or so quit holding air, i updraged to a monarch xx.. couldnt be happier!

 

[SniperGaulois]

Hi, very sorry i didn't check on this tread previously, was very involved with various technical obligations and summertime.

Here is a pic.

It's 12 years old and barely used, it's been kept at low pressure and is perhaps damaged. I would be happy to change it with a new one, except that the top fixture was very stuck, the rubber damper that holds the top bolt was so stuck, i was worried to damage it by pulling any harder. perhaps i should try soap on it.

There are many 320mm shocks online, except that all the forums told me that they don't fit on different bikes. If the travel and the fixing bolts are the same diameter and it's 320mm, i don't know why they dont fit on different bikes:

X-Fusion O2-R
manitou lrs
rockshox monarch 2.1 3.3 4.2 320mm
german A Prion (the new version of the one in the photo, which i can't find)
DT swiss 320mm
German A: Prion
Manitou 3way swinger LRS (also known as Radium RL LRS)
DT swiss XM180 LRS

i found a guy here with a lot of 320mm shocks, and my bike can adapt for 55 65 and 75 mm, and i don't think that any of these are compatible: (at end of page)
http://www.hubert-cycles.com/1126-amortisseur-vtt