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Discussion Starter · #1 ·
I thought replacing the cable on my tach might solve my jumpy tach issues, but it didn't. While I can get it to function normally--staying at about 1500 at idle--if I rev it, it goes up to, say, 5000 and then starts jumping all over the place, usually setting into some sort of rhythmic bouncing between 6000 and 9000.

I am ashamed to say I don't actually know how a tach works--it's not the same as a speedo, using a hairspring, right? Is there an electrical problem that might be the cause?

I just charged up the battery, but the bike has the old rectifier. All other electrics seem to work fine.
 

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Bobblehead said:
I thought replacing the cable on my tach might solve my jumpy tach issues, but it didn't. While I can get it to function normally--staying at about 1500 at idle--if I rev it, it goes up to, say, 5000 and then starts jumping all over the place, usually setting into some sort of rhythmic bouncing between 6000 and 9000.

I am ashamed to say I don't actually know how a tach works--it's not the same as a speedo, using a hairspring, right? Is there an electrical problem that might be the cause?

I just charged up the battery, but the bike has the old rectifier. All other electrics seem to work fine.
My CL350 tach needle jumps around in the low rpm range but smoothes out after 3000rpm.
It is the guage that is bad on my bike because I did replace the cable.
There are no electrics aside from the light bulbs in your gauges, both the tach and speedo are cable/gear driven.
 

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Both the tach and speedometer are driven by a cable that drives a magnetic disc. The shaft that the magnetic disc is connected to uses a couple of brass or bronze bushings and over time I think they get a little gunked up and sticky, causing the jumpiness. I think the only way to fix this is to spray a little contact cleaner in there then maybe a drop of very light oil. The only way to do that is to take the instrument apart which is not that tough. Putting it back together is a little more difficult.

You can see a little bit of what I'm talking about here. viewtopic.php?f=5&t=639 about few clicks down the page.
 

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Discussion Starter · #4 ·
Thanks, guys. I was hoping it was otherwise!

Since this tach doesn't work, it won't hurt to try and open it up and bring it back to life.

In the meantime, I have another tach that I bought as a replacement, only to find out that it fits a later year--looks just like the one in your pics, Mike.
 

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Bobblehead said:
Thanks, guys. I was hoping it was otherwise!

Since this tach doesn't work, it won't hurt to try and open it up and bring it back to life.

In the meantime, I have another tach that I bought as a replacement, only to find out that it fits a later year--looks just like the one in your pics, Mike.
Right you are, that's how I started opening up those things. You've got nothing to loose and lots of learning to gain.
 
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