Take the tachometer from any domestic cars, from VAZ. Inspect it. Most likely, you will see it has three connectors: +12 Volts, ground and the ignition coil. Connect it to the motorcycle and verify the operation. In most cases it will show the frequency that is 2 times less than the real.
Redo the tachometer, the essence of this process is to replace the capacitor located in the circuit of the ammeter. To do this, disassemble the instrument. Remove the three screws that are behind, then gently pry the metal braid, which keeps plastic part. She, in turn, holds the glass. Remove all three pieces at the same time, try to do it very carefully, not damaging the appearance of the tachometer.
Locate the capacitor. Most likely, it has a blue or green color, its capacity 0,22 UF. Below the device showed the correct value, you need this capacity to increase approximately two times. To do this, take a capacitor with capacitance of 0.47 UF, because the capacity of 0.44 UF does not exist. The second way to increase capacity is to connect the second capacitor with the same capacity. Find it in old TVs, tape recorders and other digital equipment.
Put back the glass cover and close the tachometer, tightening the screws. Find wire +12 Volts that comes from the ignition switch, connect it to the matching connector on the tachometer. The same procedure do with the ground. On the remaining terminal on the appliance connect the wire from the ignition coil. Ensure that this last wire went from the place where the contact of the distributor.
Check the tachometer in action. This time should be all right in the testimony. If you want even more accurate results, carefully adjust the tach trimpot resistor, which is located on the body of the instrument.