K75 speedo problem

[Wheeler]

The speedo died on my 1986 K75 a few months ago. I have had it apart twice and have thoroughly cleaned, greased (with dielectric grease) and tested (for continuity) every pin connection involved including the plug under the right side cover. Everything tests out well. I am thinking that the problem might just be the sensor at the rear hub. Is there a test that anyone may know of to determine weather or not it is working? Any info that would throw light on it would be appreciated.

[TimTyler]

How did you use the dielectric grease?

You understand that it's non-conductive, right?

[Wheeler]

I used the dielectric grease on all of the contacts (male and female) of the pins and the plugs. I tested the continuity after applying it, and there was continuity all the way from the plug under the right side cover (in the sensor wire) to the female connectors on the amplifier board of the speedo assembly. Also, the ground connections all displayed the same continuity.

[TimTyler]

Sounds like the grease is not the problem then.

My understanding is that male/female connector should be cleaned with electrical contact cleaner, firmly reconnected, and then perhaps sealed from the elements with dielectric grease.

[Wheeler]

Yes, that is exactly what I did. The dielectric grease is supposed to help fight future corrosion. I think the problem must therefore be in the sender at the rear hub or the speedo itself. Interestingly, the signal light, which is supposed to shut off after 300 yds or so no longer shuts off, so maybe it isn't sensing a signal from the sender?

[frodef]

Check the connector approximately below your right knee, on the wire coming from the speed sensor on the FD? It tends to go bad.

[Chaos]

A neat way to check the sensor is remove it from the rear end (not unplugged) and hold a 120V soldering iron close it.  The 60hz cycle mimics the sensor ring at about 40mph (forgot the exact speed)  so your speedo should register 40mph or whatever.  Sometimes the ring come loose off the gear (it is a press fit) you should be able to see if it turns looking through the sensor hole and turning the wheel.

[Wheeler]

OK I did the trick with the soldering iron and the speedo didn't register. The connector on the right hand side by my right knee is clean and working (continuity) and so it must be the speedo itself or the sensor at the wheel. I will try getting a new sensor and if that doesn't work, I will have to bite the bullet and get another speedo.

[Chaos]

Hate to see you replace parts without finding something definitive first :dunno  Is the "impulse sending wheel" solidly attached?

[rbm]

Use Karamba to isolate the problem to either the VR sensor in the final drive, cabling or speedo.  You'll need to make up a simple cable to attach your PC.  You'll be able to bench test the speedo with Karamba as well which will validate the failing part.

[frankenduck]

Neither Karamba nor a soldering iron is a foolproof solution.  Unless you have a enough of an EMF, neither will work correctly.

I have five soldering irons. Only one of them puts out enough EMF to give reliable readings and several of them don't register at all.

Same thing with Karamba.  Unless the sound board on your PC puts out enough juice you will not get an accurate reading. My desktop soundboard puts out enough EMF to register about 95% of what the reading should be.  My netbook is designed to maximize battery life and it's sound  board doesn't create enough of an EMF to register at all.

[Wheeler]

Yes, I realize that replacing a part that might not be the problem could be a waste of money. I will try Karumba and see if it will shed some light on the problem. I have checked that impulse wheel and it appears to be solid and turns with the wheel. I can't see what could go wrong with the sender or why it would fail since it really doesn't have any moving parts (other than the impulse wheel) or circuitry, and so it likely isn't the cause. I suppose any part can fail, though I have never heard of one failing. The good news is that the bike is still functional and fun to ride.

[Wheeler]

I have visited the Köcher Elektronik website, but have not been able to find a link to download Karumba. Can anyone help?

[Chaos]

I assume the odometer stopped working too.  I went a season without either because the odometer gears went bad, the speedo stopped, and I didn't feel like pulling the pod out.  Thankfully the fuel light worked!

[rbm]

I have visited the Köcher Elektronik website, but have not been able to find a link to download Karumba. Can anyone help?

Click on the highlighted "Karamba" word on the Köcher Elektronik web page upon which you landed when you selected the link in the tutorial.  That will start your download of Karamba.zip.

[frodef]

Take a ride to your closest motobricker pal and borrow a known good speedo and hook it up to your bike? And/or vice versa? That should give you some solid information.