Speedometer Repair

[CopperCollar]

My Red 79 speedometer went 10-7 a while back and I need to get it fixed. I have been trying to win a 79 speedometer on ebay but just can't compete so I am going to open up the speedometer and see whats up.

Now I have seen the speedometer innards and it looks pretty damn simple. I think the only thing that needs some deligence is the fine spring.

The rotating cup, I thought I read somewhere that it took some kind of silicone fluid??? The ones I have looked at seem to be dry. Just a rotating magnet that drives the bell if I remember correctly.

You guys have any words of wisdom for cleaning and lubing the speedometer?

Mike

[CopperCollar]

Well I have been doing some studying and it appears the CBX speedometer is no more than an Eddy Current device. The cup needs to be free of grease/oil. So I would surmise nothing goes in there else it will interfere with the Eddy Current generated by the spinning magnet.

I have my gauge apart and it looks good but there is some residue in and on the cup, the spring looks good, gears look good. The odo trip reset was glued to the threads...had to break that off so I'll be ordering up a new one.

Looks like I'll just give it a good cleaning, dry it and lube a few wear points then button it up.

A not to daunting job, getting the Bezel off without distorting it was the tough part. I developed a couple of tools for this but will need to refine them some more. Crimping the Bezel back in place is a bit of a challenge. Using pliers is one option but I think rolling the lip back down would give the most sanitary look....I'll have to look closer at how to accomplish that. Perhaps a steel roller.

Mike

[EMS]

Mike:

That is sure worth some pictures! A lot of people would love to see this. Opening a speedo is not something that is being done all the time.

[NobleHops]

Mike:

That is sure worth some pictures! A lot of people would love to see this. Opening a speedo is not something that is being done all the time.

Yes, please, a set of photos, details on the tools you made the the techniques you developed, that would be awesome.

Mike I am certain that this was recently explored and that there was a heavy silicone fluid that belongs in there. A guy said he found it at a hobby shop. Have you tried a few searches?


N.

[NobleHops]

OK, this is what I found elsewhere:

I am actually in the process of doing this repair my self. I found my cbx in the original owners garage where it had been idle since 1987. It only had 2600 miles on it. Anyway both my tach and speedo were slow movers as well. I just took both of them apart, and used both methods mentioned in the various forums. I have to say that the way to go is to take a big screwdriver and gently pry back the retaining bezel. I cut one of the yellow housings in half and got yellow shavings EVERYWHERE.

So what I found was this. There is no oil or lube in the tach or speedo. I know that there is no lube because the inside of my housing was spotless. If the bearing or cable had been leaking oil into the housing it would be thrown everywhere. Centrifugal force would splatter that lube all over the inside of that case. The bearing that the cable spins is sealed. There is an aluminum cup that is on the needle shaft just below the face of the gauge on both the tach and speedo. It has a rubber cap. Inside of this cup is a very heavy silicone that is a damping fluid to keep needle fluctuations to a minimum, just like a fluid filled harmonic dampener on engines. Over the years, or if the gauge is ever placed on its face, the silicone can seep out and run down the needle shaft towards the rotating bell. It then gets in between the rotating bell and fixed bell shroud. The gap between these two pieces is maybe 1/16". So this heavy silicone creates a drag on the rotation of the rotating bell. This needs to be cleaned out and the aluminum damping cup needs to be refilled. A lot of guys recommend just spraying wd-40 into the gauges and what this accomplishes is thinning out the spilled silicone allowing the bell to rotate again. Unfortunately, that aluminum damping cup is now empty and you run the risk of having a jumpy needle. After a lot of research I have found that this heavy silicone is actually the same as the heavy silicone used in remote control car gearboxes. I went to my local hobby shop and picked up a bottle for $4. The weight that closest resembles the original fluid is 30,000cst.

Needle removal can also be tricky. First, in zero position mark the rotating bell and bell shroud with a sharpie to establish where the resting position is when the needle is put back on. Now to remove the needle I simply hold the rotating bell with one hand and gently twist the needle with the other. This breaks the press fit free and then you can easily pull off the needle. No special tools required. When I put the needle back on I like to put just a small dab of locktite on the needle shaft to make sure that it does not work its way free.

Hope that this helps.

[CopperCollar]

Thanks Nils for the heads up on the silicone, I'll have to do this as mine is very sluggish, the tach is the worst.

The bell and cup need to be CLEAN of any lubricant. This I have learned from studying repair methods used for these Eddy Current speedometers.
as Nils said there is a cup with dampner fluid, looks like I will be going to the Hobby shob for some of this.

I am excited to get this done and tested out. I am also thinking about how to clean the white wheels without removing the numbers....perhaps it's wise to just buy some trashed speedometers and salvage the numerical wheels.

Overall the task is pretty easy, just takes the patience of a Saint. I already have the speedometer apart without taking photos. When I do the tachometer I'll be more diligent about photography and the tools I am using.

So far as I can see the only real reason to send these gauges in for repair would be parts availability and maybe calibration...every thing about them looks simple.

I found over lays here http://www.reproductiondecals.com/default_frameset.html gotta scroll down to near the bottom of the page. I can't attest to the quality though...not yet anyway.

I am not sure if Bill of Tim's CBX sells any overlays, I hear he has some new generation material though.

Dave put the speedometer of the Travesty together for me, I'd like to know how he crimped the bezel back on cuz...damn...I't looks like the damn thing was never off.

Mike

[Kool_Biker]

After a lot of research I have found that this heavy silicone is actually the same as the heavy silicone used in remote control car gearboxes. I went to my local hobby shop and picked up a bottle for $4.

Hope that this helps.

Excellent stuff Nils! We can all benefit from such research.
Aris

[Jeff Bennetts]

Good point Nils, I have always preached to store gauges, any electrical components and carbs in the position they reside on the bike for long term storage.

Once you break the seal on the needle from the shaft you can use a table fork to lift it off without damage.
you guys.

[NobleHops]

I can only take credit for remembering someone else's post . I just edited that to make it clearer...



N.

[CopperCollar]

Well I have a donor 85 mph speedo to work on. Easy enough to get the bezel off. Internals are pretty simple to.

Problem I am having is figuring how to get the odometer wheel and shaft off. Everything appears to be "staked" manipulating the stakes and the metal breaks away and I am not sure I could get everything to stay put once I assemble the componets.

The donor speedometer was covered in the silicone dampner fluid so it had been leaking for a while.

If any one has busted speedometer/tachometers that they no longer want send them my way. I'll use them in my education.

Mike