Horny speedo

[stryder]

So the speedo on my K75, (with k100, [hmm maybe rs] switches and handlebars set up) has been acting up for years now. Stops now and then, then starts back up on its own...sometimes running well for many days and rides at a time, other times doesn't work at all, or bounces up and down, start the ride working, stop for fuel, stops working etc. I tried the soldering iron tip held close to the sensor with the bike turned on and the needle didn't flinch. The blinker stays on/no self cancelling when the speedo's not working, so, gotta be the sensor, yes?

That's what I thought, but now am thinking maybe it's something else? Don't know if this has been noted/discussed before, so please forgive if it has, but I can't remember seeing it.

When my speedo's on the blink, it will pop back to life...if I honk the horn.  :Norton: Consistently...needle drops to zero, honk the horn, she pops up to cruising speed...dies, honk, lives...dies, honk lives...until it actually stays working for the duration of the ride.

Anybody see or hear of this before, and if so, any suggestions on WTF's going on? 

Thanks.

[rbm]

It's sounding like the sensor or wiring to the speedo is causing your problem.  The things to check are:

• remove the Variable Reluctance (VR) sensor from the final drive and clean it.  ensure that there are no metal particles clinging to the central iron core
• separate and clean the two-pin connector under the right battery cover.  Use a contact cleaner like Deoxit to ensure any corrosion is removed.  Examine the female contacts in the connector to make sure they make positive contact with the male spade contacts
• clean the 24 pin connector at the back of the speedo, especially pins 22 and 23 which corresponds to the inputs from the VR sensor on the final drive

These actions will ensure that the greatest strength signal will get to the speedometer.  Remember that the signal coming from the VR sensor is extremely low power -- just 1.5V p-p.  Any resistance on the wiring will reduce that signal significantly and cause the intermittent problems you are experiencing.

As for the connection with the blowing the horn, it points me to consider it a bad connection.  The vibrations from the horn could be causing the connection to make until bike vibrations cause the connection to go bad again.  I think if you wiggle the connection under the right cover, you might recreate the intermittent condition.
 
There is a PC program called Karamba available for free that can test the speedometer. You can use it to eliminate the sensor, allowing you to isolate the problem to either the sensor or the speedo.

[stryder]

Thanks for that. I too feel it's a matter of a bad connection somewhere, i.e. at times, if not working and I run over bumps or a dip in the road, it might pop back to life, though not consistently. I've tapped the pod while riding, or moved the odo adjuster and she's popped back to life too though not consistently.  I have tried cleaning up the connector which didn't seem to effect operation, and have had the pin block out of the pod after the speedo started acting up as well to work on the "choke" light connection's wire, which is always coming apart. But this horn thing leaves me scratching my bald head. It works consistently, i.e. lay on the horn, and the needle pops up to road speed right away thought it will stop working in short order. I'll have to trace the speedo sensor's wiring to see where it might run close to the horn and maybe take the pin block out again if even just to try soldering that choke light wire again, for like the 3rd time. In the mean time, if you see a black K75 fitted with an r100rs fairing blasting its horn on the 401 for no apparent reason, you'll know why.  :Norton:   

[bocutter Ed]

Are you near Toronto? I have a mosty functoning spare cluster.

[rbm]

If you're around the GTA then drop by and I can help debug the problem.

I've tapped the pod while riding, or moved the odo adjuster and she's popped back to life too though not consistently.

Have you ever opened the instrument cluster?  It can also be the connections inside the cluster between the ribbon cable and circuit card that are corroded and need cleaning.

I have tried cleaning up the connector which didn't seem to effect operation

Exactly which connector have you cleaned up?  The two-pin connector under the right battery cover?

[stryder]

Yes, I've had the pod apart several times in the past and did clean up those three pins at least once. Yes, the connector I tried cleaning up is that 2 pin connector by the battery. It still does the same thing, i.e, if it stops working, I'll honk the horn and it will spring back to life, 8 out of 10 times. The other two times, when the horn trick doesn't work, it'll will eventually pop back to over going over some road bump. Recently, it's been working 80% of the time, i.e. the speedo and horn trick. And when it is working, it's accurate...according to a Doppler radar equipped,  Minnesota State trooper that is.  :cop-car:   

[rbm]

Cleaning the pins inside the cluster most often works.  However, some have found that just cleaning may not be enough. One other trick is to very slightly twist the pins so that they press tighter against the socket contacts on the flexible ribbon.  Over time, the beryllium copper contacts lose their springiness and will not offer a good contact.  Twisting the pins about 10 degrees will correct a poor contact situation.