Small Engines (Lawn Mowers, etc.): Briggs 3.5hp blows black smoke, lawnmover, black carbon

Question
Eric, my 3 yr old lawnmover starts easy, but after running 10 seconds, starts missing and blowing black smoke. The carb is not adjustable. There is no choke ... just a primer bulb. The oil/foam air filter is clean, and this smoke continues even when I remove the filter. Replaced plug with a new one, but it quickly gets fouled up with black carbon. Muffler is also building up with black carbon. I drained and installed fresh gas, and even tried adding some fuel conditioner to see if that helped. Nothing seems to improve this. What else can I try? Thanks Bill

Answer
The black smoke indicates that the engine is receiving too much fuel.  I'm guessing you have a tank/carb assembly that is bolted together.

About the only way to fix your problem it to remove, dis-assemble and clean the carburetor and fuel tank with compressed air from an air compressor and using some carburetor cleaner.

Do you have an air compressor?
Eric