I have a murray 12hp 38 '' cut lawn tractor. When I try to start it with a key it won't do nothing, you don't even hear a click sound. I check the solenoid but I jumped that by touching the pegs and it starts the tractor. I bought the tractor from a previous owner that may have done some wiring on it. I am not sure what that little red wire does that comes out from the top of the starter may be it has something to do with that. I know the problem starts after the solenoid because that's OK.

You CAN start the tractor by touching the solenoid? THen sounds like key switch is bad.