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General Category >> Rubber Side Down! >> How [NOT] to fix a snapped cable
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Message started by Boule’tard on 01/01/10 at 22:53:22

Title: How [NOT] to fix a snapped cable
Post by Boule’tard on 01/01/10 at 22:53:22

Per Oldfeller's request, I have documented the fixing of my throttle cable, which broke right where they usually do, at the cable stop by the grip. This thread could just as easily apply to a popped clutch cable. Or as a warning to others not to try it. No way in hell would I do this much work if I could just order up a new cable from Suzuki. But this custom cable for the Mikuni VM carb is kind of a pain to replace. Also, many of you guys are way better with metals than me, and may want to save a few bucks

So after the throttle went slack and I pushed the bike home, this is what I found -- bummer:
http://i49.tinypic.com/34oo706.jpg

To make a new cable stop, I had to take some measurements of the hole it's supposed to go in. Why not just measure the cable stop that popped off? Because it was too small anyway.. loose in the hole. The correct length should be 0.29 inches.
http://i47.tinypic.com/168czv4.jpg

The diameter, thankfully, is a nice quarter inch. So I knew I could just get some round 1/4" brass or aluminum stock and not have to turn it smaller.
http://i48.tinypic.com/2n83ma1.jpg

Here I've cut a piece of round aluminum stock and ground it to the length I needed. I would have preferred brass but could not find it 1/4" or larger.
http://i46.tinypic.com/51zthy.jpg

I drilled the first hole all the way through the little cylinder. Hole diameter is just big enough for the cable..
http://i50.tinypic.com/2eezwic.jpg

Then the second hole is larger, but drilled only halfway through. This hole will accommodate the frayed cable end, encased in solder. It was 5/16"
http://i47.tinypic.com/15oigt2.jpg

Yaay, I finally got me a little $0.99 piece of aluminum! :D
http://i46.tinypic.com/33b2zig.jpg

Here's the cable, slipped through the new cable stop and frayed, ready for flux and solder.
http://i48.tinypic.com/710aj9.jpg

My little wuss soldering iron, made for circuit boards, was not going to heat the cable stop enough to melt the solder. So I resorted to a little butane torch. A propane torch would be too much, but the little butane torch did a fine job of heating the aluminum and melting the solder. I didn't get a photo of the actual soldering because I don't have 3 hands.. but you get the idea.
http://i50.tinypic.com/ei1r2a.jpg
http://i45.tinypic.com/3004av4.jpg

FAIL! >:( The solder would not wick in to where the flux was, no matter what. When I got sick of re-heating the aluminum and making little blobs of solder, the cable stop would just slide around.. or off the cable.. not good.
http://i45.tinypic.com/dwc0fp.jpg

This is where verslagen1 and others can get a good laugh.. plan B was to try to weld a little blob on the cable.. with a MIG welder designed for steel as thick as half an inch. So I set it as light as it will go (for 24 guage steel) and gave it a few short zaps.
http://i45.tinypic.com/11972i1.jpg

And damm if I didn't finally GET it, a little blob on my cable. :D
http://i48.tinypic.com/rws5qb.jpg

Of course after all the fraying, cutting, and several pops from the welder, the cable was an inch shorter than before. I figured I could compensate for that by shortening the elbow where the cable passes into the carb.
http://i48.tinypic.com/dw6f5h.jpg

There it is back in the throttle tube, "fixed!" :D
http://i49.tinypic.com/fzaf09.jpg

BUT.. unfortunately I gained nothing from this little job. All that screwing around with different methods shortened the cable too much, and I can't use it. When I installed the carb end I realized I'd have no idle :'( So my main advice is to either weld a fine bead on there with a TIG welder, or use one of those screw-on cable stops.

If someone knows of a good place to get a cable for a Mikuni VM carb (or better yet, has one to sell) I'd love to hear about it.

I hope some die-hard who knows how to solder will find this useful.

Title: Re: How to fix a snapped cable
Post by RadRacer on 01/02/10 at 03:49:14

new throttle cables are only $22 at http://www.bikebandit.com/1997-suzuki-motorcycle-ls650pv-savage/o/m6329 mine broke about halfway on cable awhile back :)

Title: Re: How to fix a snapped cable
Post by Oldfeller on 01/02/10 at 05:35:21

Well, next time I pop a cable I'll post a successful tech fix, but it just goes to prove a point that I have had made several times before over the years on other things I have done and posted fixes on -- I can do it and the instructions make it look easy. But for me it is the umpteenth time I have done it over the years so to me it is a pretty well polished trick that I can do "easy-peasy".

Then when you try to do it, it won't work out for you at all. Oh well, sorry about that, I didn't mean for you to scrap out your cable like that but stuff like that happens sometimes on these fix it up type jobs.

In this case, I know better than to try to solder to aluminum -- it don't work without very special solders and fluxes (copper/brass/steel would have been better choices) and I would have cleaned (wire brushed) the frayed portion of the cable and pre-tinned it with solder before pulling it into the hole for the final solder attempt. But that is because I have tried soldering grease laden cable materials before and I know how bitchy they can be.

If I had Boule's past experience I'd have also pre-tinned the brass/copper/steel cylinder and re-drill the through the soldered up hole so as to be just remelting some already established solder bonds on both parts when making the joint. But that would have required some prior experience to know to do that.

You'd make up your cylinder, drill it, tin it, re-drill it, thread it on the cable in the correct orientation, slide it out of the way, fray the end of the cable, spray it off with cleaner, wire brush it, spray it off again, flux it, heat it with a large soldering iron and pre-tin it, then pull the cylinder up and join the pre-tinned solder masses together. And you don't use a torch because it will kill the cable material, but I told you that beforehand.

============

To make things easier, try the JB weld trick instead of using solder. Just so the fray is large and well formed and CLEAN and the bends are sharp JB weld should be strong enough to keep the fray from bending back in and coming on through the hole. It would be less bitchy than solder, it would just take a good bit longer to harden.

JB weld has another advantage, see the blued annealed cable that Boule made with his little torch -- this would have failed very quickly because the temper was taken out of the wire material. JB weld requires no heat, so no danger of annealing the wire.

Your larger hole should be a bit bigger also, about as big as the cylinder can hold. This lets you get more fray and better "grip".

===========

Surprise. I bet every tech post on this list has little tiny bits and pieces to them that are held within the experience level of the person writing the post that don't get pictured or mentioned. That's the nature of the beast. You can only mention the bigger parts, not every little tiny thing.

This makes tech posts "dangerous" because it assumes a certain level of skill on the person following the instructions.

Since I am both kinda lazy and relatively skillful that makes my tech posts particularly dangerous to try to follow ... mebbe I should quit writing them so as to not be fouling people up.

Oldfeller

Title: Re: How to fix a snapped cable
Post by verslagen1 on 01/02/10 at 08:45:44

Just goes to show you, when trying a new skill, get a scrap piece and try it out first. Us old hands know that nothing usually goes right the first time.

Title: Re: How to fix a snapped cable
Post by Boule’tard on 01/02/10 at 17:31:58

6B4840424148484156240 wrote:

To make things easier, try the JB weld trick instead of using solder. Just so the fray is large and well formed and CLEAN and the bends are sharp JB weld should be strong enough to keep the fray from bending back in and coming on through the hole. It would be less bitchy than solder, it would just take a good bit longer to harden.

JB weld has another advantage, see the blued annealed cable that Boule made with his little torch -- this would have failed very quickly because the temper was taken out of the wire material. JB weld requires no heat, so no danger of annealing the wire.

DAMM I'm stupid, why did I not think of this! It is the perfect way for a noob to fix a cable. I did clean the cable initially with carb cleaner, which I figure is just as necessary with the solder as it would be with the JB weld.

I did not think the little butane torch heated the wire too much on the first try.. but after 5 or 6 tries, yeah that cable was pretty weak. And when that failed and I resorted to the welder, the cable was glowing red. Forget welding cables.