I've bitten the bullet and pulled my dodgy ignition switch apart to be cleaned and De-Oxitted. (Fairing off, tank off etc). While its in this state, I will replace the oil/water pump seals.

Also, over the last 12 months or so, the speedo has been behaving erratically, esp in the summer, after several hours in the saddle. It works fine for at least 2 hours, then the needle wanders down and up and all over the shop. Is it the sensor/pick-up at the final drive or in the bowels of the instrument cluster? It seems to be heat related. Before I pull the thing apart, I thought I would post, with a view that if anyone had experienced this before, what to look for. Fore warned is fore armed, as they say in the classics. I thought that it would be a good opportunity to try and get this sorted. I have access to an oscilloscope, variable power supply and audio sig gen (sine only)

Thanx, Rickmeister.

sine will do uli

probably several places to look along the path from the rear end though....including buildup of metal shavings in the rear bevel drive affecting the coil core

do you have a magnetic sump plug in there ?  many do .



good luck mate

Could it be connected to your loss of that suspension a couple of years ago? Remember that the sender unit was not that far away from the broken stud. I also had the speedo needle everywhere on the orange bike. I pulled the instruments apart, replaced dead, broken cogs and cleaned bits and pieces..no problems since....fixed the trip/odo and needle.

common problem is the three-pin connection in the instrument cluster.  
http://www.ibmwr.org/ktech/speedo-repair2.shtml

http://www.motobrick.com/index.php?topic=449.0

https://www.k100-forum.com/t4936-speedo-and-instrument-connections

Another check is to hold a soldering iron (not touch), the sensor on the bevel box.  The AC mains signal from the soldering iron should give a constant reading at the speedo. Pretty weird to see your bike in the garage showing it moving on the speedo.

http://www.motobrick.com/index.php?topic=599.0

If that shows constant, it is another indication that the trouble is the three pin connector, which is losing connection due to a bad contact when you ride.

By the way, this has happened to me, and a resolder of the three pin/PCB solved the problem.

As Charlie and Corkboy say, basic check at the back end first because it's easy.  

Mine does a similar thing sometimes, and a sharp tap on the instrument housing often fixes it, so the connection inside is a strong suspect. When I get time, I'll be dismantling that bit and checking. 

Bill

charlie99 wrote:
do you have a magnetic sump plug in there ?  many do .

Pretty sure they all have magnetic drain plugs on both trans and FD.  Every K I've ever seen has.

I vote pins in the back of the cluster.  If your odo isn't being flaky too then it's not a bad signal.

If you odo is wonky too then it's upstream of the cluster.

Thanks, Lads! I have just now removed the instrument cluster from the bike...its now on the bench.

Several times over the past few months I've tried the soldering iron at the pickup at the FD. (except, of course, when I've been out on the road when the thing goes wonky...!) All OK.

The sensor has been replaced after I fixed the the shock mounting stud.

The drain plug is magnetic, and when I drained the FD oil. the plug was free of metal debris.

It all points to the bowels of the instrument cluster.

Will read/ print out Corky's links to the repair sites. Will also investigate, while its on the bench, to set up a test jig, with my 12V PS and audio sig gen (I guess that 100Hz is about 120Km/hr)

Will keep you informed as to progress.

Thanks again.

Remember...no speeding on the bench!

Not to be nitpicky but my calculations show that 97 Hz from the sensor should read 120kph. (With minor variations for tire circumference.)

Also make sure that whatever signal generator you use has adequate amplitude. I tried it with my netbook a few years ago and it did not have adequate amplitude to read properly.

I've found the same thing to be true with soldering irons. I have several that won't even register while others put out a significant magnetic field and work well for speedo calibration.

Finally got the back off and the three pin plug thing removed.



Whereabouts is the dodgy connection supposed to be? At the bottom of the socket where the long prongs go?

Is it worthwhile to try and re-solder the pins where they attach to the PCB film?

Paralysed with indecision!!

As fer as I know, the problem is with the pins maintaining a consistent connection with their sockets, not a soldering issue. What has worked for me in the past several times is cleaning up the pins with steel wool to remove any corrosion and then twisting them 5-10 degrees with needlenose pliers.

yep that's a pretty good description of some of the issues that we suffer  duck

I resurfaced the instrument input pins  with pretty good results

also cleaned up the pins that uli has now released from their home

and bridged the connections on the film connections from the input to the electronics board ...then to the meter drive subassembly the uli has released ....resoldering can do some nasty things to the film ...unless you have a good iron

note do not try and use the new high tin content solder that is becoming industry standard now days

ive sent some images to him just now

hope it helps

Charlie...could it be the pins in my instruments that have caused the speedo working altogether?

could be stan

the motor drive wiring is the suspect area that im looking at





the rest looks not too bad

I have a big hammer which could be used....Uli can use it as well.
Does the motor drive both the speedo and the odo/trip?

have a look at the circuit stan

maybe complicated for lay people ....but looks like 2 motors to me ( I x motor ...1x guage )  but if the pins etc give intermittent operation

who knows ...  there are usually other contributing reasons why circuits stop working properly

With our climate..heat, vibration etc..no wonder problems appear with our instruments. The circuit diagram seems to mean something to you...thank goodness...but I am a lay person. Just as question...are there different diagrams for pre and post 85..when they changed the fuel lights and sender units?

yes different board and circuit ...but its found on the other side beside the tacho stan

Lads, have had a bit of success with the bench test set-up of the speedo unit.

Pin 6: +12V
Pin 13: -12V
Pins 22 - 23: Audio Sig Gen. (I/P from FD sensor)

Wound the AF up and down in frequency and the speedo followed accordingly.
Wound the level of the signal down (at 80Km/hr) until the indication became unstable. This is around 60mV pk-pk.

Left it on the bench tonight at about 80mV pk-pk at 80Km/hr (didn't want to rack up the miles too much going nowhere!)

Looking forward to looking at it tomorrow.

I didn't clean any contacts and left the two tiny retaining screws out of the of the 3 pin ribbon connector to the speedo.

Looks like one of those life support machines......you will have to make that decison at some stage.

After 1061Km on the bench overnight, the speedo was still rock solid. Admittedly, it was a cold night, no vibrations etc...but nevertheless, I'm leaning towards external, ie, the sensor and intermediate plugs/sockets.

Rickmeister

For the next bit of electronic trickery, get it to wind back 1061 km like the old technology odometers. I don't think an electric drill will quite cut it!  

Bill

Amazing how far you can go in one night when there's no traffic to contend with.

To overcome my speedo working intermittently, i followed all suggestions in the Forum with some success. So i tried this - 


- not pretty - but has worked for nearly 2yrs. It was to be temporary, something i had on hand, but the speedo behaves so i'll leave well-enough alone. 

There was a couple of mm movement of the board in its housing so inserted the rubber tube.
It looks like there is a lot of stress applied [first image] but not so, there is a slot cut along its length, just enough not to separate it, the slot fits over the board so it would'nt vibrate out [and it has'nt]

Also a bit of rubber tube over the three prongs to keep them mated.

Might be of help