blaster keyswitch

Take the ignition out of the handle bar mount. Measure the diameter of the ignition cylinder. Then us a paddle bit or hole saw bit to drill it. I think it is 3/4" but don't quote me on that.
 
Starter? You'll see when you take it apart. The threaded portion of the switch is smaller than the top of it. It has a lip on the top of it. Just measure the threaded part, drill that size hole, and drop it in. You'll be good to go.