I know that the old style "99-01 rear drives have a speed sensor on them and the newer "02-06 dont.
The question that I have is what is the speed sensor go to and what does it control ? also how did they eliminate it on the newer rears and would it be possible to go to the newer style rear and change the sensor style or machine a newer drive to accept the sensor ?
I also saw on here a post that the gear ratio changed sometime in 02 ? what were and now are the ratio's
Thanks for any input.

This is a question that I'll be interested in. I have a '01 and have seen several rear ends for later models, at a good price, but didn't think they would work.

Lewis

I own an '06

I'm not certain what you mean when you say the "old style rear drives have a speed sensor and the newer don't" - My '06 DEFINITELY has a speed sensor. Otherwise, there'd be no speed input to the electronics.

What, specifically, do you mean? The sensor on my bike isn't physically part of the "rear drive"; it's a separate component mounted on a bracket bolted to the rear drive at the brake caliper. Are we dealing with semantics here?

The change in gearing is being discussed in a recent thread, down towards the bottom.

When BMW introduced the Integral Brakes, they removed the separate speed sensor from the rear drive and just used the existing ABS sensor to measure wheel rotation. This signal is fed into the speedometer, odometer, and cruise control, as well as the ABS computer.

I don't think they changed the casting, just the final machining to eliminate the extra hole. Theoretically, you could use an older drive on a newer bike by just covering the hole, or use a newer drive by machining in the hole. Seems like a bit of trouble though, especially since drives are available used (check trike manufacturers), and rebuilding a drive often means changing bearings and not the outer case.

Hello,

I am reading your comments on the drive speed sensor with interest. I have a faulty speedo problem on my Dec 02 LT. I have examined the cable on the swinging arm as suggested on this site, and it was starting to wear. However, this is not where my fault is being caused because after ensuring that this point was OK, I still get the speedo working for a week and then not working for a week or so.

One thing that could help me to diagnose this it to monitor whether I am receiving a signal from the sensor, does anyone know what to look for? Is is simple Open / Close circuit? If so, what kind of speed is it opening and closing at, can I use a meter or would I need a scope? Or is there a voltage I should attempt to read, again can I look at it with a meter, DC or AC? Any ideas?

The reason for asking is that when it fails, it takes a few weeks to come back so it is really difficult to diagnose until I know what to expect to see coming up the wires. Of course when it is working, it is impossible to diagnose.

Finally, any practical suggestions as to how to diagnose when the bike is stationary?



Thanks in advance for your time,

Mark Breen
Ireland

I did a lot of testing of a speedo unit on the bench, using a signal generator, oscilloscope, and frequency meter, trying to determine just what all the calibration jumpers do.

You can test the sensor with a relatively high impedence analog voltmeter. The pulse train is roughly 1 Volt DC, about 4 Hz. at 10 MPH, 93 Hz. at 80 MPH. Turning the wheel by hand will certainly give you readable pulses.

An analog meter is much better to see these transitions, because you can see the needle move some at a pulse rate that would drive a digital crazy.

Hello David,

Thanks for that, I have a good quality Fluke digital meter, I think that it is more than 2 meg input impedence, so hopefully that will be OK. I agree that analog would be better, but I can try the digital. Do you think that switching it to AC might give me a reading at higher speeds / Hz?

Did you take the reading across the two wires, or one wire and ground? If so, which wire and what is the other one for?

Thanks again David,

Mark

Take the reading across the two wires. AC setting won't help, as you are not looking for a voltage reading, but looking for pulses. You need to see the transitions. If your Fluke has a frequency range, it will read that. If not, you have to descriminate the pulses yourself, cannot do that at much over 3-4 Hz. even with a really responsive analog meter.

Hello David again,

Thanks for the follow up. Did you consider any other cheap or easy alternatives to listening to the pulses? I am not sure what load would swamp the receiver of the pulses, but I am thinking along the lines of a headphone, or perhaps some type of pizo electric device that would click when the pulse occurs? But as I say, this may confuse the actual speedo electronics, however, if I thought it would not damage anything, I might consider it as a diagnostic tool, not something to leave connected to the bike in real world driving,

If it worked, I could plug the speedo into the ear phones in one of my helmets.

Thanks for your time David,

Mark

The current is pretty low, so anything added would have to be pretty high impedence to avoid loading down the sensor. Would not hurt to try a high impedence headphone element, there are some around that are in the 600 ohm range if I remember correctly. That may be high enough.

Hello David,

Thanks again for all your help, I spoke to Motobins.co.uk today and he also suggested that these electronic speedos have been giving problems for quite a few years, even on old Ks. He suggests that water anywhere will cause problems.

Did you ever consider installing an amplifier on the circuit? I know that we should not have to do this, just a thought?

Mark

The only problem I ever had was the normal cut wire where the line is zip tied to the brake line fitting. Other than that my speedo worked perfectly for 110,000 miles.

When I was doing the bench testing I found that I had to set the signal generator amplitude carefully, too low or too high would not work. It was a pretty short range of setting that gave a solid speedo indication. It was around 1 VDC. An amplifier would likely swamp the circuit.

I know this is simple, but didn't see it mentioned yet. Have you taken the speed sensor out and cleaned it?