I just answered where to get a key switch. Now that truckernix has posted it made me actually think about what may be wrong. The foot switch has a large lug contact and small contact inside. The large is to run the starter motor and the small is to bypass the resistor while starting. When foot is released, bypass is released and reverts current thru resistor to save points. So starting and then dying told Tnix that it is the resistor or it's wiring. Not the key switch. The way to trouble shoot electrical is to take an item out of the circuit, if possible, and see what happens. In this case it's easy. Jump the resistor (bypassing it) and see if it starts! Then you know it's the resistor.
If no start, short the two wires on the switch together outside the switch and try it.
It's Ok to run the motor a few seconds without the resistor.
Be sure it's hooked up correctly as Wbender says before any of this.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn