I just took apart my speedometer and I noticed that there is up and down play on the shaft which spins the needle to indicate your speed. What is weird is that when the instrument cluster is lying down with the shaft perpendicular to the table the needle sinks down about 0.5 mm or so and when I spin the needle there is a lot of resistance and the needle does not return to the zero position. When the instrument cluster is upright with the shaft parallel to the table there is no resistance and the needle moves freely. Has anyone else noticed this play? I found that I have continuity everywhere it seems there should be, yet my speedometer was not working (nor the odometer).

On my bike i have my instrument cluster angled at maybe 20 degrees from horizontal ground, which would cause the resistance I just described. So it seems to me that if there is always resistance in excess of the magnetic torque produced by the magnet, the needle wouldn't spin and, therefore, the bike wouldn't register any miles. Does anyone know if this play is normal and if it's not is there a remedy? I don't want to gut the speedometer until someone says I should.

FreebasserSF wrote:I found that I have continuity everywhere it seems there should be, yet my speedometer was not working (nor the odometer).

And you got the pulse signal from the transmitter all the way to the amplifier connection?

Inge K.

Yes, I've checked it from the transmitter to the multi pin, and from the inside of the pins to the speedometer amplifier (the three pin and the four pin) and on the speedometer unit itself. I haven't checked it from the transmitter all the way to the amplifier, which I plan to do, but assuming it makes a good connection at the multi-pin male and female, there should be complete continuity. Because of the resistance I encountered with the needle, it's making me suspect the problem is mechanical, and not electrical.

So I take it that with 57 views no one encountered this problem?

You may be a first with the problem but I have a feeling that the unit may be on the way out. Do keep us informed of any outcome.

I was thinking the same thing K. I've had the odometer/ trip meter unit out multiple times, but haven't actually taken it fully apart, to get into the area underneath the numbered gears on the odometer where the magnet which spins the needle is. As it doesn't work anyway and never has, I suppose I will crack into it and document it so I can post it here for general feedback, criticism, and mockery

I`ll guess this is a signal problem, since neither the odo or speedo is functioning......
at the end of the line it`s two separate systems.
A stepper motor for the odo, and a magnet element to move the needle.



And you got the pulse signal from the transmitter all the way to the amplifier connection?
That you got continuity through the transmitter doesn`t say that it really send a pulse signal
(but it is a good sign to that it`s alive and well)

Inge K.

Also it seems to me that the whole electromagnet driving a mechanical gear was a stupid way to go. Not only is it bulky, taking up a lot of space and requiring a larger instrument cluster, it has many moving parts prone to failure. The technology for digital meters was available in 1989, as we can see with the gear indicator and the digital clock. If they had fitted a digital trip meter and odometer, we probably wouldn't have as many problems as we do.



In this photo I have laid the cluster down and spun the needle beyond zero. This is not an action shot, it simply does not return.

FreebasserSF wrote:If they had fitted a digital trip meter and odometer, we probably wouldn't have as many problems as we do.

Haven`t got any problems with this during 26 years of ownership.

And not related to trip or odo, I also got stuck needle at my newest (tacho) when it`s got really
hot (when sunshine hits it directly for a longer time)....it`s a bearing/sleeve/bushing at the top
and bottom of the shaft....maybe it`s in one of them that the shaft gets stucked....the uppermost one seems like it could be turned.......have you tried a quarter in each direction?



Inge K

By the way, Inge, where do you get all these great schematics?

It`s incredible what could be found on the net, if you have some patience when searching........and the correct words.

Inge K.

So now that I got down to the base of the needle where I figured the play/resistance was coming from I see that there is two tightly wound copper ribbons which act a spring separated by a small gear. The copper ribbon brings the needle back to rest at zero. My hypothesis is that because my instrument cluster is attached to my bike in such a way that it vibrates a lot, perhaps some of the ribbon from one side of the separator vibrated off and went to the other side, which distorted the ribbon, and the spring didn't have enough potential energy to make it return to zero.



Also the ribbon is soldered to two terminals and another thought I had was that if the two oppositely charged ribbons were on the same side of this separator gear (for lack of a better name) then they would make a short circuit would they not?

I`ll guess it`s only a couple of springs, and not electrically connected.

EDIT: Studied some photos of the tacho (less parts, easier to wiew),
and at these photos it can be seen that the springs is electrically connected.

But no idea why they have used two springs with different diameter.
Maybe it`s someone inside here with some better knowledge about instruments have the answer to that.

Inge K.

If someone have a issue with their speedo later on and reading this thread, I`ve done a bit more research on this subject.

The moving coil elements (which is partly seen {top,left} at the first of the two above photos) is connected through the two spiral springs.

Inge K.

FreebasserSF wrote:By the way, Inge, where do you get all these great schematics?

Hi there, you can try:
http://velobanjogent.blogspot.com/2011/08/k100bmw-motometer-instruments-german.html
Best regards
JAP