I have a yardman 12.5 hp briggs.Went to put in new battery and the key was out. Then hooked up the pos cable then neg and it started by it's self with keyout and in the off position.It even started with blades ingauged. I took the ignition module off and disconnected it from harness, and still it cranks up when I touch the neg cable on battery. Any ideas on what would be causeing this to happen?

Either the positive cable is hooked up directly to the starter, the ignition switch is sending power to the solenoid or the starter solenoid is bad. My money is on the solenoid.

Thanks 30yearTech, we took the cover plate off over the forw/rev, took the solenoid off, cleaned beat on it a little, replaced it and it started normally! Will pick a new one up next time it acts up...
This is a great site, thank you again!
kevin

I've never heard of that, best that scared the dog crap out've you....would've had me wondering wtf!