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I have a new-to-me ~80's steel frame with a rear derailleur cable that is routed through the chainstay. There's a blockage close to the BB end, and I'm wondering what my options are?

My assumption is that it's mud/dirt/etc. due to where it is, the fact that I cannot blow air through at all, and what it sounds when I jab it with a coat hanger.

This frame means a lot to me, so I'm very keen to get it working if I can.

Edits:

  • The frame is a (I believe) 1981 Concorde Acquila.
  • The chainstay holds a bare inner cable.
  • And pictures added (more for Criggie, rather than solving the issue, though if click through and zoom in on the second picture you can see the exit-hole on the chainstay)

1981 Concorde Acquila frame

enter image description here

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    You could try sticking a piece of wire in an electric drill, to see if you can drill it out. – Daniel R Hicks Jun 17 '16 at 21:54
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    Internal routing was not common then. Can you tell if there's a full outer housing inside the chainstay? Or is it a terminator for the outer, and only the bare inner goes inside the chainstay? Have you removed the bottom bracket axle - can you get any access into the chainstay that way? Either a finger or a poke-wire. Sounds like a cool bike - please consider adding photos to your post. – Criggie Jun 18 '16 at 3:07
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    @Criggie Only the inner goes in, and it goes into a little steel tube that runs inside the chainstay and guides it to the exit, so there isn't even access possible via the BB shell. Current plan is try oxalic acid (which I assume to be a long shot), and failing that buy a clamp on cable stop. – tim Jun 20 '16 at 23:07
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    Can you try some air? A gentle squirt from a can of compressed air? Build up to a blast from a compressor. – Criggie Jun 21 '16 at 7:52
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    The concealed outer is sized for an innercable. So grab a spare, solder the end 5mm so that its no thicker than the cable but is solid. Then file the soldered end so its a flathead screwdriver end. Poke the length of wire into your chainstay and at the blockage, twirl it as a drill between your fingers. You should also use the wire as a gauge to show exactly where the blockage is... mark its start and end on some masking tape, so you can see if you're making progress. If you can get some particles to drop out will show if its dirt (soak with water) or rust (add CRC or WD40 and "drill") – Criggie Jun 21 '16 at 7:57
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I'm sad to say that I solved my issue by adding a clamp-on cable stop much like this one:

enter image description here.

If going down this route an optional extra is to poke the blockage with such force and frustration that your poking stick (coat hanger) breaks off and is stuck forever inside the chainstay. I elected to go down this route, but my understanding is that it's not compulsory.

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Can you add photos? If the chainstay holds a full normal outer cable then just replace it.

If the chainstay holds a bare inner cable, then it gets messy.

Can you quote the exact brand and model of frame, and our trained googlers can try to find more details?

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    See updates to answer your questions - though I have given up and added a clamp-on cable stop. – tim Sep 25 '17 at 11:38

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