Stop in for a cup of coffee

Ok, riddle me this. I put in the jumper wire. Fired right up and ran. Needed to disconnect wire to kill as suspected. Then hooked up again, started, made my throttle adjustments and disconnected the wire instead of turning key off first. Stayed running until I turned the key off. 6 more starts and runnings without a jumper needed. Key switch?
Sounds like intermittent contact in the key switch. Like TJ said, clean the snot out of it.