This flashing brake light circuit can be used for motorcycles. When brake-light switch S1 is closed, power is applied to U1 and U2. Two inverters of U2, a 4049 hex inverting buffer, are connected in a low frequency oscillator that feeds clock pulses into U1, a 4017 decade counter/divider. Outputs 0, 2, 4, 6 and 8 of U1 are coupled to the gate of Q1 through a 1N914 diode.
Schematic of the Flashing Brake Light Circuit
As the 4017 counts, it turns the brake light on and off four times and then leaves it on until the brake switch is released. The on/off rate can be set by potentiometer R2.
For best results, the on/off rate should be set so that it is rapid.