K series speedo clusters

[wightman]

The weak link in the system...BMW, it seems were too clever for their own good and the K series bikes that came out in 1983 were far more digital than their forbears. The early speedo clusters were renowned for failing within a few year of operation, generally due to ingress of water. Later models incorporated improved sealing and more screws around the periphery of the sealing backing cover. This is the cluster on my 1990, last of the pre ABS bikes and should not have been giving troubles, particularly as it only has 130000kms on the clock. But, as Goldy will attest, the copper tracks breakdown and can be gently repaired by adding small quantities of hot solder to the broken tracks. Brian Roberts. up in the hills was a very knowledgeable gent, who would take a dicky speedo unit and repair all the faults, usually for a case of beer. Unfortunately Brian passed away and that avenue is no longer available. I did, however remember him telling me of an old trick to twist the ends of the 24 pins, which have rectangular heads, so that they make a more forced point of contact with the female sockets, on the end of the wires feeding to the speedo cluster.

My speedo suddenly stopped reading kph, which in turn stopped the odo numbers tumbling and the auto-cancel on the indicators to kick in. First, I cleaned the pick up on the top of the final drive; clean as a whistle and applied some electrical contact cleaner to the brown/yellow wire connector just behind the RHS side cover but the speedo was still stubbornly not working. I opened up the back cover and it smelt like that virginal, clean electrical smell that often emits from brand new toys when you open the battery compartments. It was dry as a bone and all the tracks were in perfect order. Taking a baby long nose pliers, I twisted all 24 pins about 20 degrees towards the starboard beam and pushed the two white connector strips back into place. Put the whole lot back together and its been sweet as a nut since......

[Bozo]

John

Very impressive...I have not twisted on my pins since Dire Straits were in the top 40. Twisting may improve neuroplasticity.

Bozo

[KoosWA]

The exact malady that the Grey Mare is currently suffering from ['96 vintage - 20 years old this year, should say Grey filly really]. The speedo struggles to keep up all the way up to full gallop when it seems to catch up and read true. Actually I think it is reading true by looking at the other traffic, but will have to test with the GPS.

The odo is reading about 9 % under, therefor I thought my consumption has increased by about .5 l over 100 km.

I am intending to investigate and fix the speedo this weekend, so your tips are timeous.

I have cleaned the pickup and checked the connection under the right side panel - also the location of the "other" shonky connector of the fuel pump [Coincidentally no issues with that one for months now..., probably just jinxed it].

I have been putting off tampering with the instrument cluster, but will implement your fix now.

PS: so the digital pick up rotates the odo as well?

[wightman]

Hallo Koos. Yes, the odo tumbling relies on power getting to the speedo needle first. The only combination you can have is the speedo needle working and the odo not tumbling (which is almost invariably those white plastic cogs turning to cream cheese). Before you dive into your cluster, remember that Goldy changed the final drive on that bike (he put a K100 one in) so that is why it may be underreading. If it is consistently reading 9% down don't mess around in there, as those tracks are delicate.

John

[KoosWA]

So what is the fix for the under reading - a K100 cluster?

I still have the weak signal to speedo issue. From the sound of it the under reading can be caused by the inaccurate signal as the speedo is indicating slower than the actual speed and the odo tumbles slower as a consequence? Is my thinking right there?

[wightman]

Maybe Koos. Definitely on R series, the odo gets its signal from the gearbox output shaft (bevel gear off it) and hence the speedo must be calibrated to the final drive ratio. With the K, the sensor is on the rear hub, and may be reading actual wheel rotations, which could bypass all different drive shaft options. If your problem is intermittent, the twisted pin method should work. If the underread is constant, I have a spare K100 speedo (off a 1986, pre ABS model) which you are welcome to try (and keep if its better than yours)

[wightman]

Hey Koos, twist your pins (like we did last summer)

http://www.google.com.au/url?sa=t&rct=j ... qk5EPda2aA

[KoosWA]

Can't remember last summer!