new tach cable, still doesn't work

[Alex M]

My tachometer stopped working one day, all of the sudden. Turns out the cable was snapped in half.

I replaced the cable today, but the tach needle will barely budge, despite engine speed. I pulled the cable out from the tach gauge and it spins slowly and fast, in accordance with engine speed.

I read some old posts where BikeCliff recommended turning the tach upside down and spraying lube in. I did this with WD-40, but it still doesn't work.

Suggestions? Thanks!


(working on an 81 GS750E)

[twistedwankel]

I read some old posts where BikeCliff recommended turning the tach upside down and spraying lube in. I did this with WD-40, but it still doesn't work.

Suggestions? Thanks!


(working on an 81 GS750E)

Lucky for you the tach's are relatively cheap to replace. The speedo is the one that you can't find or get fixed anywhere. Are you sure you are spinning it in the right direction? Only goes CC on mine. When I put some silicone in mine and worked it in rotating with a small screwdriver until moved freely it took weeks for it to start working properly again...dragged...and hung up. Then fine again.

[Alex M]

Are you sure you are spinning it in the right direction? Only goes CC on mine.

I wasn't spinning it myself. I meant that I unscrewed the cable from the gauge, and saw that the cable was spinning when the engine was running. So it seems that the gear is seated well to the Cam, and that the problem is with the gauge.

Do you mean I should turn the gauge upside down and work some silicon in? Any brand you recommend? I don't have any here.

Is there a way to test the gauge using a small screwdriver?

[Alex M]

Update photo



any suggestions? how closely are part A and B supposed to touch?

[Redman]

I cant answer your question about part A and B. Actaully have never seen inside of a tach. Thanks for the picture.

One thing I can say from experience is that you cant spin it ("A" in your picture) fast enough by hand/fingers for anything to happen. I have tested tach (and speedo) by using a wooden matchstick in a varible speed drill motor. You say you have replaced a broken tach cable, maybe if that tack cable is still available you can take out the cable cable and use part of that rather than a wooden match stick.

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[tarantula]

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any suggestions? how closely are part A and B supposed to touch?

I had just opened up my tach today to inspect it since it was making shrieking noise. I also got to wonder how does it actually work. I'm pretty sure there is no physical contact between those parts. I think that rotation of the bottom part creates a small vortex that puts force on the top part in proportion to spinning speed, which moves the dial further or not. I'm sure someone with a degree in physics will laugh at this and give a proper explanation. If two parts were actually touching, considering that one rotates and the other one never goes beyond the same 270 deg or so, there is no material in the world that could withstand that without wearing out quickly to the point that two were not touching any longer.