well, that is the nature of that engine. Check the air filter and im sure the carb is running rich. Make sure all the extra oil on the air filter is sqeezed out. The L head engine burns dirty but it is reliable. The engine temps cook dino oil into submission but hey what do you expect from 20 oz of oil that is heated to its limits and beyond. Dont worry, what you are expiriencing is normal for your engine and the oil. The design of the L head allows for the oil to absorb dirt and carbon and to hold these in suspension, while the engine is in use, which is what oil is supposed to do. The aluminum block rapidly transfers heat out to the atmosphere and inside to the engine oil, which is what cools the engine on the inside. If your oil is dark after a few hours then it is doing its job. Change the oil every 20-30 hours and it will be ok. These engines are durable and run for years with proper maint. The L head design runs even longer if you dont maintain it. My Dad never changed oil on our old briggs push mower he just added oil to it once in awhile. We had that mower for 16 years. The intek engine burns fuel more efficiently and the ohv design allows for better fuel economy and combustion versus the L head design, but unfortunatly water is not an approved lubricant for the Intek engine.