Craftsman lt2000 18hp. 917.273751 Ohv starts and runs good for about 6 mins and then cuts off. New gas cap. Good gas flow to carb. I checked coil when engine stopped and ohm read 13k, cold reading was around 9k. What should a warm coil be reading if good? Noticed motor tried to rev up as it was dieing, but only for about 2 second, then motor stopped. Any ideas.