Speedo Failure

[Gerbil007]

Blimey, I seem to be racking up problems faster than I can fix them!
My speedo has suddenly failed on me. It was working fine on friday night, then Saturday morning, nothing. Needle wont budge and the mileage isn't going up. I had the bike de-servo'd recently. Could that have anything to do with it? (Although speedo worked just fine for a few weeks after this was done.)

[David.]

I had the bike de-servo'd recently. Could that have anything to do with it?

The speedometer is activated by the speed sensor located in the top of the final drive unit housing, behind the drive flange.

The cable runs on top of the paralever arm adjacent to the rear brake hose. The cable may have become dislodged/damaged whilst having the servo removed.

[Gerbil007]

Thanks David, I'll have a look when I get home. Would speed sensor failure also cause Odometer failure? My mileage isn't going up.

[David.]

Would speed sensor failure also cause Odometer failure?

From what I've read elsewhere, the answer would be yes.

[Marcosalopo]

I had two of these sensors go on my 2005 bike,  so sounds like problem.

[rangemaster728]

Since you recently had the wizzy servo system removed, consider this...if you find the front sensor has not become dislodged or unplugged:

IF your bike was produced prior to Aug 2006 the front AND rear wheel speed sensors are BMW p/n 34 51 7 666 436.

(New price for the sensor is about $300 USD - but I am certain you could find a good used one somewhere for a fraction of that cost.) There is something else you could try...

Since you no longer have ABS, consider removing the rear sensor and putting it on the front. The ABS system works by comparing the front and rear wheel speeds, hence the two speed sensors and rings on the wheels.

If your speedo now works, you’ve found the problem...and since your ABS is defeated, you should not need a rear sensor.


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[David.]

The speedometer is activated by the speed sensor located in the top of the final drive unit housing, behind the drive flange.

This quote was taken straight out of the Haynes Manual.

As both speed sensors are the same, would removing the suspect rear one and replacing it with the front one do the trick.

[rangemaster728]

This quote was taken straight out of the Haynes Manual.

As both speed sensors are the same, would removing the suspect rear one and replacing it with the front one do the trick.

Yes...see my post above.


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[David.]

Since you no longer have ABS, consider removing the rear sensor and putting it on the front.

If your speedo now works, you’ve found the problem...and since your ABS is defeated, you should not need a rear sensor.

The speedometer is activated by the speed sensor located in the top of the final drive unit housing, behind the drive flange.

[Gerbil007]

Hmmm. So I replaced the rear speed sensor this afternoon. Speedo still dead. Does this mean that the front sensor is the problem?

[rangemaster728]

Wait..what??

Sent you a PM on this as well, but just to clarify did you remove the rear speed sensor and put it in place of your front speed sensor?

That’s what we’ve been suggesting, to see if your front sensor (which drives the speedometer and odometer) is faulty.

To review:
1. Remove front wheel speed sensor.
2. Remove rear wheel speed sensor.
3. Install the sensor you removed from the rear wheel of the bike on the front wheel.
4. Test ride.
NOTE: I did some more testing, see my post later in this thread (#21). The assumption that the front speed sensor feeds the speedometer and odometer is incorrect. My mistake!

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[rangemaster728]

Another question comes to mind – you said the bike was recently “de-servoed”...Out of curiosity, did the person or shop doing the modification leave the ABS electronics module in the bike?

It’s necessary to leave it in so your speedometer and odometer works, among other things.

The assumption here from your initial post is after the modification the speedometer and odometer still worked, but failed sometime after.


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[Gerbil007]

Ah, right. It seems I've misunderstood and not quite understood. What I've done is to just replace the rear sensor. I haven't swapped out with the front. Guess I'll be busy on monday then!

[Gerbil007]

The assumption here from your initial post is after the modification the speedometer and odometer still worked, but failed sometime after.

Correct

[STeinar]

My speedo has suddenly failed on me. It was working fine on friday night, then Saturday morning, nothing. Needle wont budge and the mileage isn't going up. I had the bike de-servo'd recently. Could that have anything to do with it? (Although speedo worked just fine for a few weeks after this was done.)

Most often I have found that the cable from the real sensor is broken. Stripset to hard to the chassis - and when the rear is bouncing up and down - the cable breaks inside the outer isolation.  Follow the cable carefully all the way - take off the strips / fastenings - and feel the cable with you fingers - moving it slowly .  Or if you find a place where there are deep marks in the rubber/plastic - cut it and re connect it properly - remember to make it really watertight