Sears lawn tractor with a Briggs 20 hp engine that has no spark what should you check you have tried everything but with no change what can you do?

unplug the wire that is connected to the coil. {not the spark plug wire} the small wire that goes to it. and see if it starts up. if so you will then have to pull the spark plug wire to shut the mower off. make sure that you pull it with a rubber glove on so you don't get shocked or you can pull it with a pair of pliers that are insulated. if that works. shut off key. plug the small wire back up and then look at the wires going to your starter where they "plug" together. unplug and turn it around, then plug it back together. that should work. if you have unpluged any of the wiring and plug it back together, you may have plug it in backwards. I DID {lol} hope that helps Take care