I have a problem with my Suzuki GZ250. Sometimes it will start everyday and run like a top. But then some days it will not start and has a different (muffled) sound when turning over. After a few days sitting, it will start again and run just fine. It keeps doing this and I have replaced just about everything in the carburetor. It has a new fuel filter, spark plugs, premium non-ethanol gas. Any ideas or suggestions?