These step-by-step instructions for removing and disassembling your Mini's speedometer were posted to the Forums by Mini_fly. This article is particularily useful if, like many, you have an odometer that's stuck trying to turn over a lot of 9's.
1. Remove the air cleaner assembly. Be careful not to drop anything into the carb. Remove speedo cable and disconnect the wiring harness in the back of the binnacle. Do not remove the bulbs and wires from the back of the binnacle yet. It is hard to see things in here and you may get the wires and bulbs mixed up.
2. Disconnect the Oil pressure gauge line. Do this where the pipe that comes from the gauge connects to the hose in the engine compartment. It's rather difficult to get at the back of the gauge to remove it there and the pipe is flexible enough that you can keep it connected. Also remove any screws that hold the pipe in place in the engine compartment
3. From inside the car, remove any screws that hold the binnacle to the body.
4. Pull the binnacle forward into the car. You may have to do some twisting and turning and hold your tongue just right to get it out. Remember that the oil pressure pipe may catch so you will have to be careful to bend the pipe in a more friendly shape.
5. Once you have the binnacle out of the car and on a nice clean workplace, you may continue. You may want to set the face of the binnacle on something soft so you do not scratch the chrome ring.
6. Take a picture or note where all of the different bulbholders and wires go on the back of the head. Remove all bulbholders and wires from the head.
7. The screws that hold the binnacle are set into the clips on the side of the speedo head. You will need an angled screwdriver or similar tool to remove them.
8. Once the speedo head is free from the binnacle, remove the outer chrome ring by bending the edge of the ring so it is true again. You should be able to slide the ring from the head. Be careful that you do not bend or damage the speedo needle or the needle keeper pin at the 0MPH mark.
9. Remove the two screws from the back of the head. This will free up the center dial of the speedometer face. Take note of where the needle rests when it is free of the keeper pin. You will need to place the needle back in the same place when reassembling. This will keep the speedo somewhat in the same calibration (I think).
8. Carefully remove the needle. This may be accomplished by prying up on its base near the shaft it sits on.
9. Remove the two screws in the face of the center dial. This should free the outer and inner faces from the odometer assembly.
10. The odometer assembly may now be carefully cleaned with some clean compressed air. You can make an adjustment to the numbers by turning the spindle they ride on with a set of pliers. This is what I had to do with mine to get it to go from 84999.9 to 85000.0. This is a common problem from what I have read. The innards of the odometer get worn and cannot move all of the dials when it comes to this point. Further disassembly will not be covered here.
11. The speedo can be tested at this point with a Robertson screwdriver bit (square) placed in a drill. Insert the best fitting square bit into the back of the unit where the speedo cable goes. You can observe the operation of the various components inside the odometer and speedometer and check for wear.
12. Reassembly is basically the reversal of disassembly. Just remember to set the needle in the same spot that it was in when you removed it. Also, when offering (I’ve always wanted to use that term) the binnacle back into the car, connect the wiring harness before installing the screws and oil hose. Check that all of the lights in the binnacle work, IGN, HB and the Turn signal indicator. Also the fuel gauge and the dial backlights. Then finish the rest of the connections making sure to properly clamp the oil pressure pipe to the engine compartment and connect the hose securely.
13. Start engine and check for leaks. Take the car out for a test drive and give yourself a pat on the back for a job well done!