I have 2004 21 horsepower Craftsman V twin lawn tractor. The other day I started it up and ran it to mow the lawn, it didn't sound right so I stopped, remover the spark plug and it was fouled. My question is will it leave any crap in the cylinder or valves. I got new plugs and started it up, it sounded a little funny , but then started to clear itself. I haven't used it since, so I'm wondering will it it get better the more I use it?