Flaky Speedo Fix


From: Rob Lentini
Date: Wed, 8 Mar 95 10:10:54 MST
Subject: BMW: Motometer Fix

Dan Eggert asked what can be done to fix Motometer speedometers on Ks:

Dan, I had numerous (I think 4 or 5) speedometer failures soon after I purchased my K75S new in '87. Nothing really fixed the problem until Iron Horse in Tucson replaced the entire instrument module under warranty. New modules are identifiable by two small Gore-Tex vents on their undersides.

Assuming you've got the older type and can't get it replaced for free, try the following:

Intermittent speedos are usually caused by a fault in the internal connector to the speedo subassembly. Remove the entire module from the bike and lay it on a towel, face down on your work bench. Remove all the perimeter phillips screws. Remove the module back cover being very careful to not damage the gasket. With the speedo to your right, you will notice a plastic arm with a printed circuit run that plugs into the speedo input connector. The speedo female-side contacts are usually the culprit. Corrosion can form between the male pin and female contacts, or the female contacts lose spring pressure on the male pin. What you've got to do is separate the connector, carefully bend the female contacts tight again, and reassemble with perhaps just a SLIGHT amount of copper anti-seize compound on the male pins to assure long- term continuity.

At this point it will be easy or hard on you. Early speedo connector arms had a service bulletin performed that actually called for sawing the arm in two, then cementing the connector to the speedo with RTV. If yours has had this done, you should be able to carefully pull the connector back and off the speedo to service the contacts. If the arm is unmodified, you will need further disassembly including removal of the instrument assembly from the bezel cover, and them removal of the speedo module itself--all this to get to the contacts! It can be done, requires patience and dexterity, but if you're intimidated by all this have your dealer do the procedure. Hell, he may get you a new cluster courtesy BMWNA just to avoid the hassle of working on yours!

The new Gore-Tex Motometer modules supposedly have improved contacts, and the speedo connection is screwed onto the rear of the speedo, eliminating (or at least greatly reducing) vibration-induced loosening the the connector. My new module has been very reliable. I've only been into it to replace a burned out bulb.

Good luck!

Rob Lentini
'87 K75S
Tucson, AZ


Date: Wed, 8 Mar 1995 15:15:41 -0500 (EST)
From: Charles Goodspeed IV <CGOODSPE@CAIS.CAIS.COM>
Subject: BMW: Re: BMW K75 Intermittent Speedometers

I have experienced all of the intermittent problems previously mentioned regarding the speedo on my K75. I have taken it apart, cleaned everything, to no avail. I finally found that the little connector that is located under the right side cover, a 2 pin connector, was crudded up, thus the intermittent problem. I cleaned it and voila it worked, for a while. The next time it went intermittent, about 1 year later, I took apart the speedo unit, and noticed black corrosion between the 24 pins on the back of the unit, and the flexible copper circuit tape. The solution to this it to scrape away the corrosion, very carefully, and buy some rear window defrost fix-it paint from your local auto parts store, and paint each pin carefully. Let the paint dry, and then make sure the paint between adjacent pins is scraped away, or you may get a short. It this doesn't fix your problem, I would be very surprised.

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Charles Goodspeed                            6300 Georgetown Pike
SAIC                                         McLean, VA 22101
703-285-2081
89' K100rs
86' Husky 510TE
72' R60/5
86' 535i
..........you were really flying when I passed you!

 

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