Speedo Problems, Anybody?

[jgalle]

My XJ's Speedo is tearing up cables. When we put a new one in, it ran for about a block, then the speedometer ran high, and quit. (We did not rev it up, was cruising at normal spped down block)Checked it out, cable was snapped. Metal shavings were in the speedo assembly. Put another gauge cluster in, and same thing. We have bench tested it to 60 MPH on a drill, but it keeps doing it when everything is connected together and riding down the block. Getting a bit tired of buying new cables for tests, so if anybody has any ideas, I am open for help. Still have a few days of warm weather here in Texas, would liek ot take advantage of it.

[strom]

Check the cable routing. There should be NO sharp angles and stuff like that. Did you change the cable or the entire thing, with the outside tube thingie and all?

LP

[Ken Talbot]

Check that the inner cable is not too long for some reason. IIRC, when it has been fastened at the bottom, the end of the inner should only just barely protrude past the screw fitting on the top end. If it is sticking out even another half inch or so, it might be digging into something it shouldn't.

With the cable fully installed, put the bike up on the centrestand and block the front wheel off the ground. Spin the wheel as best you can and listen closely at the speedo. Using a drill would tell you the speedo is working, but it won't give you the closest real-life condition.

[skids]

Re: Speedo Problems, Anybody?

Originally posted by jgalle
My XJ's Speedo is tearing up cables. (snip)

Is the female end at the speedometer head free turning?

[Jerry]

OK. Here goes. "Inside the XJ Speedometer.":



Speedo cable turns 2 items in the speedo unit. First is a gear that drives the odometer and trip odometer. 2nd item is a magnet.



The silver 'bell' twists with the magnetic field generated by the speedo magnet. The speedo needle is coupled to this secondary magnet through a spiral spring.



A mechanical reset, when pressed, sets the trip odometer back to all zeros.

What seems to happen.....
I've had problems with the mechanical reset mechanism. Age and rust tend to make this mechanism very sticky. The resistance eventually wears the plastic gears in the gear train, or the worm gear that transfers the speedo cable movement into the gear train.

I put a small amount of white lithium grease (applied with a jewler's screwdriver) to all pivot and wear points in the reset assembly to free it up to like new condition. In addition, a tiny dab on all gears doesn't hurt.

My current speedo, 3rd in 2 years, works very well after taking the time to clean and lube it. I removed the reset plunger assembly as well to clean and lube the shaft and other wear points. In all, takes about half an hour of labor after you get the speedo out of the instrument cluster to complete the clean and lube.

Note: Pictures are of the 2nd speedo that died. If you look closely you will see wear on the worm gear assembly.

The sending unit, on the front axle, should also be re-lubbed every now and then. Mine had run dry, and was making noise. Not difficult, though you have to remove the axle bolt, take the assembly apart (1 snap ring) and clean and re-lube the main drive gear shaft.

[fgcox1]

Sppedo Problems

How in the world to you get the mechanism out of the plastic part? I have looked at everything I can think of and cannot find how to disassembl.

Tnx Fred

[jgalle]

I do not have the bike with me, I have been with a mechanic trying to fix it together. We did change the tube along with the cable both times. I do not know if the cable was OEM, or if it was Universal. So it may be that is is too long. I am going to get the Speedo Assenbly from my mechanic tomorrow, and I will see if I can tell where the metal shavings are coming from. That might narrow my search a little more. I am just irritated at this point. Spent almost as much money on the speedometer assembly as I did on the bike itself.

Trying not to sell the bike, or cut it up and sell it in pieces. Thanks for all the help, will take some pictures as I work on it tomorrow.

[Jerry]

I just removed the screws that I could, took things apart and cleaned them, reassembled with a bit of lubricant. Didn't totally disassemble the unit.

In my case, the rod for the reset had built up some rust and wouldn't slide smoothly through the guides. I took some steel wool and 400 grip sandpaper and very carefully rubbed the shaft until it was clean. Had to partially push the shaft down (in) to get the whole thing clean. Lubbed it just a bit with the white lithium grease.

I put a bit of grease on all gears and pivot points but none near the indicator wheels or the shaft they ride on....was afraid the grease would end up on the numbers.

[fgcox1]

Speedo

Anyone know how to get a 79 Special speedo open? I have it out of the metal can but no clue how to procede. It lookes like you might be able to go through the faceplate if you can get the glass off but the plastic ring is holding it on and no sign of a release. There are two screws on the mechanical cable connector but they appear to just hold it stable to the housing.

Anyone?

Tnx Fred

[Dragonrider]

You have to dremel the back edge of the faceplate ring off . . . carefully. Then you can glue it back on when you are done.

[jgalle]

I was just thinking. The first cable to break was the one that came on the bike when I bought it. And I didn't have problems until those winds threw my bike 3-5 feet across the ground. The next day, I did a run-over, and everything looked ok. (besides the turn signal that looked like a tin can that rolls open) I rode it half-way down the block, and that was when my speedometer jumped to 60+ and then quit. (The cable snapped) Maybe something is pinching the cable from the fall, or I don't know, but I am going to have to get dirty on this one. Since it does fine until I ride it, maybe pressure from sitting on it is messing up the cable.

So many maybes, and it is too stinking cold to play with it, and those speedo cables are running me $10-20 a cable. Ouch

[crunchbird]

Well, there is no physical connection between the cable and the needle. The cable turns the magnet that is inside the bell-shaped thing (jerry's second picture). The magnet must spin really fast for a moment for the needle to jump to 60. It seems like the cable is binding and twisting, then breaking loose.

[jgalle]

Ok, I know the problem, know for the fix.

The Problem is the Cable Worm in Jerry's second picture. (Would use mine, but the batteries died, and nobody replaced them) The teeth in it are the shavings I found on the magnet. The Cable Worm seems to not be moving at all, and now it has been shaved down to nearly nothing. I will have to purchase another Speedometer, but I have one in my sights as we speak. Hope to buy it in about 2 hours.

What is this White Lithium Grease? I need something to help the Cable Work turn freely to prevent it from locking up again.

I am hoping to get the speedometer Friday, and get my bike back in working order then also.

Thanks for all the help, maybe this will give others a chance to get in their assemblies and lube some parts up. Seems as though this particular does not have any bearings. That kind of sucks, but I guess having an XJ is worth the hassle right? it is right?

[crunchbird]

For another problem, while Jerry's fine pix are up...some people and I had the problem that the speedo was bogging down, reading too low. The problem is the bell-shaped guy needs lubing. If you pop the rectangular electric part off the back of the speedo you can direct oil past the magnet to the shaft inside the bell. The arrow in the 2nd pic is pointing exactly the way you need to aim. This might save having to do a complete teardown.

[Jerry]

2 items brought up in the past few posts....

White lithium grease is a water repellent, high pressure grease. It is available in most auto parts and hardware stores. The most convenient form I've found is a small tube available at Sears in the garage door opener area, where it is sold as a lubricant for garage opener rails. I also have one grease gun filled with it. Grease comes in one of those cardboard tubes. Grease gun is one of those 'compact' types to which I've replaced the stock steel nozzle tube with a rubber one.

Getting the speedo out of the XJ instrument pod is a fairly lengthy process, as you have to remove the entire instrument pod, digital readout and all. If you have a fairing, as I have, it can be done with the fairing in place but it helps if you have a 90 degree ratcheting phillips screwdriver. After the pod is off, 6 (?) screws hold the case assembly together. Remove these screws and remove the top of the case. 2 more screws hold the speedo assembly in place. Remove these scresw, pull the dash lights out of the back of the unit, and it comes right out of the case. Looks just like the photos....

Couple other comments. Indicator needle is mounted on a splined shaft. Can be gently removed if you put pressure on both sides of the shaft. Then you can remove 2 small Philips screws and change face plates, or get deeper into the speedo itself. If you remove the needle, make some kind of line-up mark on the siver 'bell' and the rest of the speedo. I found out the spiral spring needs some pre-load or else it will read fast. Believe me, it is no fun taking the speedo apart again to try to different pre-loads to get an accurate reading after not making note of it first time through......

One other note concerning the cable...I had several failures of the internal cable until I replaced the whole assembly. Did an autopsy on the old cable housing (outer part) and found the crimp at the lower end had partialy failed, and there was a 'lump' inside the housing that was literally rubbing the cable. Defect was not visable from the outside. My theory was the lump was causing the cable to bind, causing erratic readings on the speedo, and eventually causing the cable to break at that spot.