Originally Posted by K100Dennis
I think I read here somewhere that the only fix fot the later models is to remove and reset the needle position. Is that correct ? If so, does the needle just pull off the shaft (I assume so) ? Mine appears to be over-stating by approximately 8%, e.g. 120 Kph on the speedo is 110 Kph by my GPS.
There are 2 ways to correct the problem:
#1 - Is use a GPS
#2 - Here it comes....
Vic Agresti posted the following in the 'Hall of Wisdom' on the main board:
Correcting an inaccurate K1200LT speedometer requires access to the back of the speedometer and soldering two tiny jumper wires on specific points.
The speedometer can be accessed by removing the instrument cluster -- then with it sitting on your bench, separate the cluster halves and access the speedometer. OR, you can separate the cluster while itís still in the bike, and remove the speedometer that way.
Randy posted instructions (and photos) on fixing the speedometer without removing the instrument cluster here.
The procedures to access the speedometer by first removing the instrument cluster:
Iíve fixed two K1200LT speedometers after first removing the instrument cluster. I prefer this approach because it seems less likely (to me) to lose or drop something from the (very expensive) cluster. On the 2nd LT where this procedure was used, the very long O ring between the cluster halves came off. Had the instrument cluster not been sitting flat on a bench, it would have been impossible to properly position that O ring to allow reassembly.
It's not difficult to remove the instrument cluster; it just takes time. These procedures assume you have followed the directions in the repair manual to remove/reinstall the cluster. (The odometer reset button unscrews, which the manual doesn't tell you!)
Carefully remove about 25 bulbs/wires from the back of the cluster. The manual has an excellent wiring diagram at page 62.5-- so, you don't have to write down where the bulbs and wires came from. (There is one omission on that page however, the ďextraĒ green/black wire is attached to the terminal just above lights 19 & 20.) Lightly reattach the screws after you remove each wireís terminal, as those screws also hold the instruments into the cluster. Once you have the cluster face down on your workbench (laying on something soft), remove the back panel. There lies the speedometer circuit board (it's quite small, maybe 2.5" square).
WARNING: Be careful when removing and replacing the tiny bulb sockets on the back of the cluster. Several folks have managed to break the filaments in the bulbs and didn't notice until the bike was back together. Replacements from BMW are $2.50!
To fix the speedometer error, solder a tiny wire jumper between the two points at the JB location on the back of the speedometer, and at the two points at the JC location. After doing that, if you have new Bridgestone BT-020s, the speedometer should then be accurate. With other tires, the speedometer should still be within 1%. Refer to the photos in Randyís post, of the speedometerís circuit board to see the soldered-in jumpers. (This is actually the REAR of the speedometer.) Take a close look at the JB & JC location and you'll see the tiny wires.
Use a 15 watt sharply pointed soldering iron designed for electronic work -- Radio Shack sells them for about $8. A 25 watt iron is TOO HOT and the tip is too large. Cut two 2" lengths of 24 gauge (that's REAL small) solid copper conductor and tape a wire over the JB points. Made sure the wire is actually touching the existing soldered locations so you don't have to hold the wire down while you're soldering. Use a very thin ROSIN core solder. DO NOT USE ACID CORE SOLDER! For soldering tips, refer to: http://www.aaroncake.net/electronics/solder.htm
Let the soldering tool heat up completely before you start. Then, very carefully touch one point of the JB terminal with the ironís tip, then barely touch the existing soldered area with the tiny new solder . Should take less than 5 seconds per point. Use a VERY tiny amount of solder per point. MUCH less than a single drop. Once you've soldered each of the 4 points, use a small wire cutter to clip the excess 24 gauge wire. If it doesn't cut all the way through (since it should be touching the circuit board), work the wire back and forth until it breaks off. Lightly push on the wire at each location with a small screwdriver or other tool, to make sure it stuck. That's it, you're done.
If the inside of the cluster face plate is other than perfectly clean, now is the time to clean it. Iíve found that car polish (not wax) can be used to bring plastic back to a clear/clean state.
An optional additional modification is to solder one wire of a two-conductor (small gauge) pair to one point of the JA jumper and the other wire to the other JA jumper point. Then, run this wire THROUGH the back of the instrument cluster (or install a connector, so the wire can be removed). Connect these wires to a SPST micro switch that is accessible with the bike fully assembled. If the JA is jumped (switched closed), that will reduce the speedometer reading by another 1%, giving some flexibility depending on your tires and their wear.