'79 Speedo Clean-up

[vwbug7777]

I took my speedo apart yesterday to fix a "sticking" problem. After reading as much as I could on this forum I decided to tackle the job and just get it done.

Speedo.1.jpg

Removed the 4 nuts and rubber inserts on the back and lift the housing clear.

Speedo.2.jpg

Speedo.3.jpg

The trip winder unwinds in a clock-wise direction and then the guage slides out of the front of the cluster housing. The chrome steel ring slides off.

Speedo.4.jpg

To remove the black steel bezel that holds the glass onto the yellow body took 15 minutes of gently prying up a section at a time with a screwdriver until at last the glass can be gently lifted out -(sorry no photos of that as I needed 2 hands and a sense of humour ). The yellow housing that holds the speedo unit is slightly flexible and that helps getting the bezel off.

Speedo.5.jpg

Speedo.6.jpg

You will notice that when I carefully moved the needle round to 20 mph it stayed there for a while before creeping ever so slowly down to zero. That was the problem I had come to fix! Undo the 2 rear screws and, without touching the needle or face, carefully withdraw the unit out of the housing.

Speedo.7.jpg

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Here are the innards.

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This is what you see. The speedo drive comes up from below (in the photo) and has a magnetic steel disc on the top. That rotates inside, but not touching, an aluminium cup that is directly attached to the speedo needle. What you cannot see in this photo (but will on the next post due to photo upload limits) is a steel backing plate, the same shape as the aluminium cup but only covering the lower half. That is very close to the cup and any sticky fluid or oil in there holds the cup stationary while the spinning magnet is trying to drag the aluminium cup around the disc. I wiped the residue off with aerosol contact cleaner until I could move the speedo needle up to 140 mph and it would return smoothly and immediately to zero. I did not replace the clear gel-like fluid that had leaked onto the cup because the needle was moving nicely. Also I did'nt want to tempt fate and perform more surgery on this unit! I had no need to remove the needle or face of the speedo but could have quite easily at this stage. I put it all back together in the reverse order, the bezel shows no sign of open heart surgery at all and it now works A couple of hours well spent.

[NobleHops]

Great content, thank you very much, including for the excellent photos.

N.

[steve murdoch icoa #5322]

Thanks for the great write-up, Andy.
So, you weren't tempted to "massage" the odometer reading while in there?

[tevan]

Could you please give me a little more detail on taking the ring off. Also how do you go about putting it back on without screwing the ring all up? thanks and by the way that is a great article you wrote up. VERY HELFUL INDEED.. thanks

[cbx6ss]

thank you kindly for the procedure and pix! Very helpful!!
/r
Brad

[vwbug7777]

Hello Tevan, the bezel is curled over the "yellow" casing by about 1mm, and that makes it kind of tricky to bend straight. If it was longer it would have helped...but the trick is to try and squeeze a small screwdriver, say 3mm wide at the tip, between the lip of the ring and the yellow casing. Place the guage face down on a thick towel (prevents damage) and try to lever up one piece about 1mm then move around another 3mm and do the same again. After about 10 minutes you will question your sanity for tackling the task BUT a little at a time and after 3 or 4 complete revolutions the lip will be high enough to get needle nose pliers onto and go around again straightening it up until you can prise out the glass. The reverse is to press the raised lip down A lttle bit at a time with the wooden end of a small hammer, sort of just leaning on it and move around the ring. Finally, I had a well worn pair of large pliers and placed the lip in the towel material and gently squeezed the lip down more. It will never be perfect but the rubber cushion that the guage sits against hides any small wrinkles. I suppose patience is the key here - "slowly slowly catchy monkey!"

[tevan]

Thanks for that reply. I have a s l o w tach and am thinking on tackling it. Have you any tips on fixing a slugish tach?

[Kool_Biker]

Here are two mostly self explanatory pics I am sure I have picked up from a forum thread in here.
And as the saying goes, 2 pics are worth 2 thousand words ..

IMG_3260.jpg

IMG_3252.jpg

But I have a question for you Andy:
I always thought there IS some silicone fluid in theses gauges to aid with the damping of the pointer needle.
In your excellent write up, you have REMOVED old silicone which should, or should not, be there.

After the operation, you report the gauge seems to work OK. But have you tested it in road conditions, what's the needle damping like ON THE ROAD?

Cheers, Aris

[tevan]

Yes those pictures are allot of help... thanks

[Jeff Bennetts]

Yes those pictures are allot of help... thanks

I posted those pics awhile back, one other tip is that if you wish to hide the re-crimped bezel altogether you can get an extra Crome beauty ring that the gauge sits on and turn it upside down on top of the existing ring, it's lip will cover the black bezel a few mm's and hide the crimped lip.

Picture a 2nd chrome ring upside down facing the gauge on top of the original ring, use the 4th pic in the 1st post above for a reference.

[Kool_Biker]

I posted those pics awhile back

As always, well done Jeff! We all benefit from your experience.
Aris

[vwbug7777]

Those two photos of Jeff's explain it really well - what a great idea to use a large hose clip!!! Damn, that would have helped me alot...ha ha!
You know, when I buy a drum of Jet A1 at the airport, they use a crimping tool to fold over the sealing cap over the opening lids. Now .....if that were the same size as the CBX gauge diameter all we'd have to do is get someone to make up hundreds of the rings, uncrimped, and the CBX community would be safe for decades! I'll have to look into the crimping tool more closely next visit.

[vwbug7777]

Here are two mostly self explanatory pics I am sure I have picked up from a forum thread in here.
And as the saying goes, 2 pics are worth 2 thousand words ..

IMG_3260.jpg

IMG_3252.jpg

But I have a question for you Andy:
I always thought there IS some silicone fluid in theses gauges to aid with the damping of the pointer needle.
In your excellent write up, you have REMOVED old silicone which should, or should not, be there.

After the operation, you report the gauge seems to work OK. But have you tested it in road conditions, what's the needle damping like ON THE ROAD?

Cheers, Aris

I have not yet road tested it - I twirled a screwdriver in the speedo to see it swing up, so to answer your question, I don't know what effect it will now show on the road.

[vwbug7777]

Hello All,

A quick note to say that I have tested it and it works fine - no lag and no shake either, just very smooth.
The hard thing now is to see the speedo "kmh" on the inner ring ("mph" on outer) when pulling away from the lights -it accelerates so well once you hit 4000rpm that I'm at 100 before I can focus on the dials, in a 70 zone! Need to put some lines of colour at 70 and 100 on the dial or I will not have a licence for long...!

[Tripnut]

Great post. Helped me a lot.

PO bent put a huge dent in the bezel and now I have to fix it.