The microswitch is installed on the right side of the cylinder head cover. The movement of the pushbutton is obtained by an arm having a wheel in contact with a small support “adjustable by two nuts” fitted on the rod driving the throttles on the carburetors. On the distributors there are two breaker points: The R2 operates until the microswitch opens the circuit (about 3000 r.p.m.) and the R1 begins to operate over 3000 r.p.m.. The microswitch opens the circuit causing the R1 breaker point to operate when the accelator is pressed and the engine speed is 3000 r.p.m.