I have a John Deere X534 riding mower with 375 hours on it. This has a Kawasaki FS730V engine. Everything was good until about 300 hours, when, while mowing, it would suddenly die after about 30-minutes. It would not restart until maybe 30-minutes later, but it would then only run another few minutes before dying. Sometimes it would back-fire randomly as it was dying or while trying to restart. This did not happen every time, but as time went by, it happened more and more until this scenario would happen every time the mower was used. At about 370 hours, I did the following: Replaced fuel filter and fuel lines, replaced air filters, replaced fuel pump, rebuilt the carburetor, replaced both magnetos and spark plugs (magneto gap at 0.008"), cleaned the solenoid on/off valve located at the carburetor, and cleaned all engine cooling fins. By the way, this model does not have a vented fuel cap. The fuel tank is vented by a return line from the carburetor/air inlet. Since these things have been done, I do notice that the mower starts easier when cold. However, it still does not work properly. As an example: Yesterday while mowing, after about 30-minutes, it started stalling preparing to die, but if I immediately shut off the mower it would recover and I could then continue mowing. This process repeated itself every 10-mintes until I finished mowing. This morning I used it for an hour spreading fire ant bait. I then removed the spreader and attached my sprayer planning to spray some weeds. The engine was still hot and it would not start. I am sure if I give it a 30-minute break it will run just fine and I can spray weeds. Any ideas here?