theres a "pump" if ou want to call it that.. its like a small disk in a round thing not sure whats its called ,,, but as the vacume pulses it acts as a pump... not sure if it works or it was was designed to work but dosent ... i dont know i was younger when we raced them and didnt do shit to the karts my self but put the tires and motor my dad built on and raced... he did all the tecnical stuff...