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Dissassembling speedo

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drooartz

drooartz

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Am I right in thinking that you have to remove the trip reset knob in order to take the speedo guts out of the case? The little set screw in the knob of my new speedo is stripped (and in there good). Due to the size of the hole, I'd figure I'd have to cut the knob off to get it removed! Any ideas?

This isn't critical, since this is (supposedly) a working speedo. I was just interested in cleaning and oiling it up before putting it back in the car.
 
Interesting, I'm tearing apart a bugeye speedometer too, although mainly just to find out how it works and maybe have a good spare.

I found some info in the MGA Guru web site about this, https://www.mgaguru.com/mgtech/dash/st200.htm. It says to pull the right side of the speedometer face forward until you can get in behind it with a small screwdriver, then you can get at the split pin that holds on the trip reset shaft. I couldn't do this, however, with mine. Even if I could, it seemed it would be impossible to get it all back together.

So, I took off the pointer and the face. This worked, but now I have to recal the thing. It also becomes very easy to wreck the spring, which I nearly did.

By the way, I was able to remove the knob from mine, but that didn't help. The arm is still too long.

So, that's as far as I got. Sorry, I know this is probably not very helpful, but take it for what value it may have.
 
That is not a set screw in the trip knob, it's a roll pin.
Drift it out with a nail or somthing like that.
It also helps too remove the dial before trying to extract the guts with the trip arm.
And if all else fails, you can always redrill the trip arm and stick a new roll pin in it should it break off like mine, it's just a little shorter but still works.
 
I was able to get my 2nd speedo (Tunebug's original) partially apart. Finally got the bezel off, and got the knob off as well. I've run into the same issue you have, Steve. That arm for the reset knob has to come out before the assembly can be removed. Not the brightest design, though now maybe I understand why I see speedos for sale that are missing that knob and arm. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
 
That makes sense, Frank. With the face in place there's just not much room to work. I'll go back and play some more...
 
Well, gave up for tonight. I was having trouble getting the needle to come off, and didn't want to break anything. I'll try again at a later date.
 
The pointer is hard to get off. The plastic part is attached to a brass counterweight, and the brass part is press fit onto the pin. It has to be pried off, but you must be careful to pry under the brass part, not the plastic, and do it from two sides. Sometimes an ordinary table fork makes a good tool for this, if it fits. Otherwise, a pair of 1/4" screwdrivers can be used.

Actually, the knob on my speedometer is held on by a screw, looks like an 0-80. So apparently these were done a couple of different ways.
 
Before you get much further into this, download the 27 page PDF by Anthony Rhodes on Repairing Jaeger & Smiths Speedometers. I found the following link for the document:
https://mywebpages.comcast.net/rhodes/speedo.pdf
This is a must-read when working on mechanical tachs and speedos.

Take photos of the process in the event you can't remember how it came apart. Work on a clean, white cloth on a flat table to catch parts. Most importantly, have fun.
 
Oil in the speedo. I had bad luck with that. Cost me a speedo and a cable. I havn't read the PDF mentioned above but the last time I had to take mine apart I cleaned it all and put it back together dry. Partly because that was the way the first one was before I decided to oil it. It's been that way for about six thousand miles and I havn't had any problems at all. By the way the second time I had a problem was with dry graphite. Just my two cents.
 
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