I have a 5 year old Toro LX426 that has been a great mower until recently. On Saturday I was mowing the yard and it started to make loud popping sounds (almost like firecrackers) and then I started to lose compression. I changed the spark plug, oil, oil filter, fuel filter, and air filter, but it didn't help. The engine is cranking and I am getting sparks, but it isn't turning over. Any ideas before I have to take it to a service center and spend money I really don't have?