I would say to clean out your carb, if you found debris in the petcock then there is a good chance you may have something in your carb. Once you clean it then ride it and see how it runs and if you are still having problems I would play with the jetting a bit, I dont know your altitude or anything but stock jetting can cause problems. Get the spark plug diagram and see how your air/fuel mixture is and take it from there. Also be sure to keep your air filter clean.