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PostPosted: Fri Apr 12, 2013 8:54 am 
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Joined: Sat Jun 26, 2010 11:07 pm
Posts: 1901
Location: brighton
There are a few of us with these forks in various states of disrepair. Mine's the Obsys55 from a 97 Xchox.

viewtopic.php?f=1&t=251731&p=1888066#p1888066

I'm going to need to decide whether to attempt the repair (I always prefer to salvage than replace but I've never done even the slightest work on a sus fork before) or just get a rock shox or something. I'm guessing it'll be a question of getting seals - or is it possible my fork can be made to work without any replacement parts? Can generic parts be used?

The seller said it worked last time it was used but after a long period of storage its gone completely flat.

There's a useful looking repair guide in the link above - in french! Might attempt a translation.

The bike's in my Grandpa's garage so no pics for now I'm afraid. Except this one:

Image

And this:
Image


Last edited by jaypee on Mon Aug 17, 2015 3:27 pm, edited 1 time in total.

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PostPosted: Sat Jun 15, 2013 5:48 pm 
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Joined: Sat Jun 26, 2010 11:07 pm
Posts: 1901
Location: brighton
Sending the link to a mate so I'm adding an extra pic

Image


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PostPosted: Sun Jun 16, 2013 6:04 am 
Retro Guru

Joined: Sun Aug 16, 2009 5:13 am
Posts: 485
Location: Canada
55 Obsys


Attachments:
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1370853714061.jpg [ 25.61 KiB | Viewed 938 times ]
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PostPosted: Sun Jun 16, 2013 8:34 am 
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Joined: Sat Jun 26, 2010 11:07 pm
Posts: 1901
Location: brighton
Nice one thanks. Are these decent forks? The little I can find on these bikes suggests people liked the ride generally.

Will they be similar to other forks of that era and type
in terms of repair and maintenance or am I just letting myself in for lots of hassle?

Seems I can pick up working RS indie for £20 or Judy for £40 or mozo pros for something in between. So maybe I should just ditch these old sunn ones for being broken, obsolete and obscure.

But I'd much rather keep the bike original and have it how Sunn meant for it to be ridden - unless that's just a really bad idea for reasons someone might be able to tell me?


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PostPosted: Mon Aug 17, 2015 3:35 pm 
Retro Guru

Joined: Sat Jun 26, 2010 11:07 pm
Posts: 1901
Location: brighton
So I've finally got round to this one. I've found a few useful guides online. I'm stuck on how to pump it up however. It uses a football type needle adapter. The official guide I've found says it's a delicate operation and that you need to move the needle gently from side to side to avoid breaking valve. I can't figure out if you're meant to push the needle right through the rubber valve or if the valve has some kind of mechanism that means you don't need to do that.

No air seems to get through which makes me think I need to push the adapter right through, but if that's wrong I will have punctured the valve and I doubt I'll find a replacement.

The valve looks like a little ball from the underside (last photo) and when you push the needle into it you can see that it's slightly split (third photo) but seemingly not the whole way through.

Another consideration is that if you are meant to push the needle right through it looks as if no-one's ever pumped the forks up before.

The need goes in the little hole at the top (maybe that's obvious)

Pics in a secondImage
Image
Image
Image
Image


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 Post subject: Re:
PostPosted: Tue Aug 18, 2015 12:00 am 
Classified Mod / Lincs, East and South Yorks AEC
Classified Mod / Lincs, East and South Yorks AEC
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Joined: Tue Apr 01, 2008 5:45 pm
Posts: 6010
Location: East Yorkshire
Apply a little grease to the needle and push it all the way in, start with about 40 psi and see how they feel.


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 Post subject: Re:
PostPosted: Wed Aug 19, 2015 6:04 am 
Retro Guru

Joined: Sat Jun 26, 2010 11:07 pm
Posts: 1901
Location: brighton
Thanks Chris, will do!
(not wishing to doubt you but are you pretty sure on that, not just a guess? I'd hate to put the valve beyond use.)


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 Post subject: Re:
PostPosted: Wed Aug 19, 2015 6:38 am 
retrobike rider
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Joined: Fri Aug 08, 2008 2:36 pm
Posts: 16747
Location: Yorkshire, England
It's a guess but they are the same as rockshox mag and did fork valves.

Hence stick it through.

It may well be damaged already, I may be able to repair if no luck doing it yourself.


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PostPosted: Thu Aug 27, 2015 8:32 pm 
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Joined: Thu Aug 27, 2015 7:26 pm
Posts: 253
Location: French Alps
Saw a repair site somewhere who recommended drilling out the cap at 8mm and (pretty much) forcing an automotive schrader into the resulting hole. It's a bit of a last resort, I'd have thought, there's a good chance of fouling it up properly, and even if you get it right you've "ruined" the vintage resale value, but could be done.

Ah, here it is. In French, can help with translation if Google doesn't do it for you.

http://xcrosseur.09.free.fr/Vtt/meca-obsys55.html


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 Post subject: Re:
PostPosted: Tue Sep 01, 2015 8:30 am 
Retro Guru

Joined: Sat Jun 26, 2010 11:07 pm
Posts: 1901
Location: brighton
Good stuff, thanks. Actually I found that and it was a useful guide (the best I found) to stripping the fork down. The conversion is a last resort as you say but good to know it's an option.


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