Small Engines (Lawn Mowers, etc.): 12hs bs kill wier, simplicity lawn tractor, safety switches

Question
Eric,  My '89 B&S 12hs,(md#281707, type #0125)on a,
Simplicity lawn tractor (md#1691340), doesn't always start.  I found
that if I                 
disconnect the kill wire from the magneto the engine runs just
perfect.  I thought the ignition switch might be the problem but
when I plugged  in the new one, all I hear is a click after a few  
seconds and the breaker blows. If I put the old switch back in,
the engine might start with kill wire  connect or else I have to
disconnect the wire to start it. All the other safety switches seem
to work. Except the engine starts with the brake bail in ether set
position or released position. If there is a safety switch
connected to brake system , I cannot seem to find it. Any ideas
what the problem might be?  

Answer
If you have a single pedal for the brake/clutch then there should be a safety switch on the pedel or on the neutral transmission position.

Have you cleaned the mower and inspected for bare wires or missing parts?  I've seen some safty switched completely missing from the mower.
Are you dis-connecting the kill wire from the engine block terminal?
Let me know.
Eric