I have been pulling my hair out over this 'overheating' (?) John Deere. It has a Kawasaki 600V-as21 engine and will shut down usually after 15-30 min. mowing. My first thought was coils. I bought new Kawi coils. same result. I removed anti-backfire solenoid. same result. I replaced spark plugs with new and colder, pulled sheet metal and blew out around engine, adjusted valves, installed larger fuel filter, cleaned carb., and even sharpened the blades. Is it possible a safety switch could be cutting the spark out after heating up ? I just ran out of options ...