I have a neighbors lawn mower here she asked me to look at it. it runs for about 15 minutes and then it dies. if you try and restart it it dies if I let it sit for a while it will start and run for 15 minutes and then it dies this is one of the newer overhead valve models with the thermostat I want to make that's my problem be fore I start buying new parts for it I don't have any used ones in my junk pile as I haven't had to work on only a few of mowers with this engine