Either the switch is shorted or the wire from the battery is shorted to the wire that feeds the "on" position of the switch. Disconnect the battery and then disconnect the wire from the battery where it connects to the switch. Use an ohm meter to measure continuity on the back of the switch with the switch turned to the "on" position. Measure from the battery terminal (on the swithch) to the run terminal. The problem is probably the switch and not the wires, the ohm meter will tell the tale.
Remove wire from switch "M" pole. With switch in OFF position there should be continuity from the M pole to engine block.
If switch checks ok, then trace wire that was connected to M pole to the magneto kill lead wire.
When switch is in OFF position the magneto kill lead should be shunted to the engine block thus killing the engine. Please comment here with model number for further assistance.
Answers & Comments
Either the switch is shorted or the wire from the battery is shorted to the wire that feeds the "on" position of the switch. Disconnect the battery and then disconnect the wire from the battery where it connects to the switch. Use an ohm meter to measure continuity on the back of the switch with the switch turned to the "on" position. Measure from the battery terminal (on the swithch) to the run terminal. The problem is probably the switch and not the wires, the ohm meter will tell the tale.
Test switch and wiring for failure or short
Check ignition switch.
Remove wire from switch "M" pole. With switch in OFF position there should be continuity from the M pole to engine block.
If switch checks ok, then trace wire that was connected to M pole to the magneto kill lead wire.
When switch is in OFF position the magneto kill lead should be shunted to the engine block thus killing the engine. Please comment here with model number for further assistance.
Check wires going to key switch