A crank start ignition switch is a switch that has a feature to engage the starter on an electric start motorcycle. Insetad of just turning the key to 'on', you turn one click further to engage the starter and hold it as the bike 'cranks over' and starts up. As it starts up, you let go of the key and it stays in the 'on' position. To turn the motorcycle off you turn back to the 'off' position. This style of switch helps simplify a motorcycle electrical system, as you do not need a separate 'starter' button in addition to the key switch.