Sudden loss of spark? briggs 21 hp.

The way that this engine is turned off is to ground the wire to the ignition module. This is located under the flywheel shroud bolted next to the flywheel, as the flywheel spins this module makes electricity and stores it till the magnet on the flywheels trips it and it dumps its electricity out the spark plug wire. It is everything that has anything to do with spark. that little ground wire on it is what shuts it off. this ground wire is ran in series through many safety switches including seat, blades,transmission,brake and also the Key switch.If everything is right this will allow the little wire to be ungrounded and it will have spark.I feel to make this story complete ,when the key is on there is also electricity through the key switch from the battery feeding the fuel solenoid on the bottom of the carburetor which will also shut of the engine from the lack of fuel but has nothing to do with spark but one more pain in the safety nightmare.Short of throwing money at this mower you need to know if it is one of the safety or key switch or if it is the ignition module. Remove the flywheel shroud, unplug the little wire , it should be a flat spade , turn it over with the key and see if you have spark. If you do then it is the tractor safety's or key switch . Let us know at the end of your test. Briggs and Stratton Modules