Small Engines (Lawn Mowers, etc.): Briggs & Stratton 28R707 1120-E1, briggs stratton, piston rings

Question
recently found fuel in oil. Drained completely installed new inlet and needle in carb. Engine started but exhaust was blue, so let run for five minutes and exhaust eventually corrected itself, no blue smoke. Mower for about 20 minutes then blue smoke returned but this time very very prominent. though maybe muffler might be coated on inside with oil/fuel residue but don't know how to pull to check. what else other than piston rings should I be worried about and how to check without overhauling. Thanks

Answer
Make sure your crankcase isn't overfilled. Most crankcases hold 20 oz. of oil. If it is overfull, it will seriously damage your engine. You can check the compression which should be anywhere from 60-80psi. Anything lower will tell you that the rings are wearing out. Also, make sure that the breather tube is not plugged.