Small Engines (Lawn Mowers, etc.): Brigs Ignition Problem?, briggs stratton, john deer

Question
I have  John Deer L120A lawn mower with a 20 hp Intek Twin V OHV. I was running it and noticed a slight miss. As things progressed it become worse and worse to the point it would not run. Once cooled down a tad it will fire back up but run very rough and steadily decrees rpm to the point it will die again. I removed both coils (I was corrected later by being informed they where in fact magnitoes) I cleaned and reset the gap using a business card. This did not correct my problem. In fact I had difficulty get it to even start. I found that if I remover the plug wire from the plug on the left side it will fire up with a miss, where it would not with both plugged in. If I unplug the right wire from plug it will not fire up at all. I do show spark on both plug wires. Thanks for any help...

Answer
I would start by replacing the coils.  It sounds like you're getting hot in breaking down.  You could check with a local Briggs & Stratton Master service dealer to see if they have the coil tester provided by Briggs & Stratton.  I hope this information helps.