I have a craftsman garden tiller with a briggs&stratton intec 6hp engine with overhead valves.I recently had a problem with the carb and replaced the float,needle,seat and all gaskets as well as a thorough cleaning.Now, my carb is flooding again and gas is getting in the crankcase.What does this mean?

If the carb isn't flooding, replace the OIL BREATHER. This is not the air cleaner. Locate it at www.searspartsdirect or Home - Briggs & Stratton

Well, you should remove and clean the fuel tank, and lines, and the carb now again. Inspect the lines for any break down, change fuel filter. Sounds as though you have microscopic particles in the fuel and it is holding the needle open. Or perhaps you bent the float while repairing the first time and it is not allowing the needle to seat all the way.