K Bike Speedometer Calibration
K bike speedometers usually run about 10% from the factory and it's just plain annoying - at least to me. Based on the IBMWR tech pages, I have my speedometers recalibrated so that they are just a wee bit fast. That way, in a 60 mph zone, when the speedometer is running at indicated 70mph I'm actually doing 68-69 mph and not breaching the 10 mph over common speeding ticket threshold. With a GPS, it's fairly simple to recalibrate your speedometer.
Tools required:3mm and 5mm Allen wrenches
Phillips screwdriver
Small flat jewelers screwdriver
Handheld or other GPS device
Soldering iron
Here's how to do it:
Get a recalibration reading: Remove the speedometer sensor from the final drive. Turn the bike on. (It doesn't have to be running.) Hold the soldering iron near the speedometer sensor. The speedometer should now read at about 45mph or so - the speed associated with the 60 Hz magnetic field generated by the soldering iron. (US and Canada electrical systems are 60Hz.)
Go for a ride: Taking a handheld or other GPS device with you, go for a ride. Get the bike going a constant indicated 45mph (or whatever your recalibration speed was) and look at the speed on the GPS. (Usually about 41mph.) That is what your real speed is when the speedometer sensor is at 60Hz.
Remove the instrument cluster: Remove the four 5mm Allen bolts on the back of the instrument cluster that hold the instrument cluster in it's bracket. (You'll need to remove one of the side panels for a K75S - a major PITA.) Then, depending on the year, there is either a Phillips screw or 3mm Allen bolt that holds the wiring harness connector to the back of the cluster.
Remove the instrument cluster back plate: Place the instrument cluster face down on a towel or something to prevent scratching it up. Depending upon the year, there are either 7 or 9 Phillips screws around the perimeter securing the back plate. There is no need to mess with the ones in the middle of the back plate.
Remove the "guts": There are six screws that hold the guts in the instrument cluster - four at the middle bottom and one on each side. Remove those six screws, turn the cluster over and carefully shake the guts out - pull out the trip odometer know as far as it lets you while doing this - there's a notch in the side of the speedometer face plate which lets it by the trip odometer rod.
Warning: Be very careful with the instruments once removed. Try not to get fingerprints on the face plates and be very careful with the speedo and tach needles - they will fall off if you look at them crossways.
Loosen the speedometer from the assembly: There is a very small black screw in the white plastic in the lower outer corner. That will loosen the speedometer assembly from the rest enough for you to gain access to the potentiometer which controls the speedometer.
Locate the small potentiometer: The arrow below shows the potentiometer that controls speedometer calibration.
Adjust the potentiometer: Usually, using a jewelers screwdriver to turn the potentiometer counterclockwise about 45 degrees will get the calibration pretty close.
Test and adjust the calibration: Remove the speedometer sensor from the final drive again. Hook the instrument cluster back up to the bike, turn the bike on and place the soldering iron near the speedometer sensor again. The speedometer should read close to what you found was your true speed with the GPS (e.g. 41mph). Perform minor adjustments to the potentiometer as necessary until you are satisfied that the speedometer is calibrated to your liking.
Another Warning: If, when testing, you misalign the connector pins on the instrument cluster when hooking it up you can fry your $75 Bulb Monitor Unit in the relay box.
Reassemble: Reassembly is simply the reverse of disassembly. Be sure to remember to pull the trip odometer out while sliding the guts back in.