Topic: Speedo not working but odometer still working

[azuredesign]

I went out for a ride today and noticed that my speedo was not working. Unscrewed the cable, that's turning fine, and the odometer is working. Can anybody tell me what I'll be looking to replace when I open the speedometer up?

Thanks,
Ben

[Bodi]

There's nothing really replaceable in there anyway...
The eddy current clutch has seized, probably just needs cleaning and lubrication. There's a magnet assembly turned by the cable, the odometer is geared directly off the shaft this turns on so I can't see a way it isn't turning. Around the magnet is a metal cup that's attached to the speedo needle, with a watch spring holding it back at the zero mark. The turning magnet induces an electric "eddy" current in the cup metal which makes it act like a very weak electric motor, there's not much force to turn the cup against the spring so dried out lube in the tiny bearing on the speedo shaft is the usual problem. Just soaking it in isopropyl alcohol (didn't remove the odometer numbers on any I've tried, other solvents may) and trying to get a drop of clock oil (or MMO) into the bearing is all I can suggest. Simply filling the speedo through the light hole with isopropyl (99%) and shaking a while usually gets them working. The pure alcohol should dry spot-free on the inside of the glass, if it leaves spots they are the remains of dissolved gunk from the speedo insides: draining and refilling the thing 3 or more times should leave pure clean isopropyl to evaporate cleanly. This avoids the nasty process of opening and resealing the speedo case.

[azuredesign]

Thanks alot for writing Bodi, I'll try as you suggest. I did note that there was a whining noise with the cable attached to the speedo. All this time I thought it was a dry cable and kept lubing it. The noise was gone on Thanksgiving day and the speedo was working fine. Now just the noise remains. I'll clean and lube through the light hole and see what happens.
Thanks again and all best,
Ben

[Paul]

I have similar issues on speedo's before.
It could also be just wear'n Tear.

In my case the Clock worked, the cable worked but when joined, the play between them was too much, I ended up putting a small wrap of insulating tape around the squared end of the cable to get more of a tight fit into the clock, worked so well, never wen't at it again.

[azuredesign]

I have similar issues on speedo's before.
It could also be just wear'n Tear.

In my case the Clock worked, the cable worked but when joined, the play between them was too much, I ended up putting a small wrap of insulating tape around the squared end of the cable to get more of a tight fit into the clock, worked so well, never wen't at it again.

Man, I'm all for easy to implement suggestions. Thanks!!

[jtb]

Ben, I've got a speedo from a 750 K7.  the outside ain't so good. but it works.

[Dennis]

Hey Bodi, where are you getting that 99% isopropyl alcohol?

I like to use it for similar purposes. Lately can't even find 90% only find that 70% crap.

Can you provide any helpful hints? Thanks!!

[Jonesy]

Can we also add this cleaning method to the "Tips 'n Tricks" section?

[gregk]

Bondi

I tried the alcohol on my tach and its like new. 

Thanks for the tip

Greg

[Bob Wessner]

I believe the later tachs/speedos have glass lenses?? Anyone tried this on earlier instruments with the plastic lens?

[azuredesign]

Thanks for bringing this up Bob, as I'm on a '73.

[bbrown]

I had a tach. that wouldn't work and found that the pivot for the needle shaft was out of round due to wear! i mixed up some jb and repaired pivot. as jb started to harden, i kept moving shaft to keep it from siezing, 1hr. later fixed,has been working for 3 years with no problem. Bob

[BobbyR]

There is another thread with pictures on taking the speedo and tach apart. I did it on a on old beat up set and it does work. I had some issues re crimping the back. I have a bit more work to do on that. If I cannot resolder them I will seal hem with JB weld. Very simple mechanism. The oil and grease harden over time.