There are some courses that are adjustable, that is, in the back of the clock they carry a ruletite with several positions and numbers 4,6,8,12 ...
These tales are those that are installed for marine diesel engines and agricultural machinery and public works. They carry the regulation because unlike yours, they are connected to the engine alternator and receive a variable number of impulse per return, (hence the numerites).
For four -cylinder online gasoline engines, (such as yours), the Vuelta account always receives two impulses per crankshaft, so that they are not adjustable.
To know if you tell the revolutions, it is trusted, place the dot in Hz, and between the signal cable (the same of the clock) and mass, accelerate and compare with the following measures:
1000 rpm = 33 Hz
1500 rpm = 50 Hz
2000 rpm = 66'6 Hz
3000 rpm = 100 Hz
4000 rpm = 133 Hz