When you rev your Harley Sportster it keeps on cutting out?

Stock Harleys come out of the showroom with fitted with a rev limiter that cuts the ignition out at around 5600 rpms. Gets kinda scary when you overtake a truck and halfway there the motor starts to cut out. Can be overcome by fitting an aftermarket ignition module that will rev out to about 7000 rpms.(more than enough for a harley)