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On the inner workings of speedometer cables

KevinGlover

What does this wire do
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Hey team,


My speedometer isn't working. I have an '81 Honda CB750. I looked at the drive gear and it spins freely and the teeth are good. I think it's an issue with the cable.

Here's what I've noticed. If you stick a flathead into the wheel end of the cable and twist it, the square peg on the far side doesn't twist. *however*, if you twist the cable housing that inserts into the drive housing, then the square end that goes into the speedometer turns.

So that's what I'm confused about - if you twist the housing, it works. If you twist the actual cable, it binds.



Can anyone explain to me why it's doing this?


Kevin
 
Cool, thanks AMC. What do I need to know to get the right cable? Do they come in standard lengths?

And if you do feel like bothering, I would like to know why it does that when it's broken.
 
In a mood to discuss it now, my bad.

The inner driven cable is in essence a super long spring, it's wound in coils. To allow drive with some cushion from the spring effect, pretty much all long gauge cables do that. When the cable outer housing runs dry of lube then the cable drags to often tear in half, and depending on how that happens the spring coils can break clean or more likely the spring unwinds to be too big and at least one half of it then sticks the broken end into the outer housing to be locked to it instead of turning free. Why I said pliers, pull cable out and likely torn in half.
 
In a mood to discuss it now, my bad.

The inner driven cable is in essence a super long spring, it's wound in coils. To allow drive with some cushion from the spring effect, pretty much all long gauge cables do that. When the cable outer housing runs dry of lube then the cable drags to often tear in half, and depending on how that happens the spring coils can break clean or more likely the spring unwinds to be too big and at least one half of it then sticks the broken end into the outer housing to be locked to it instead of turning free. Why I said pliers, pull cable out and likely torn in half.


AMC, that makes really good sense. Thanks for the information. There's a motorcycle scrap yard near me that I'm going to go look through, otherwise I'll go for eBay. I think I'll take your advice and pull out the cable to get a look at how it works and how it broke.
 
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