Small Engines (Lawn Mowers, etc.): excessive oil back to carb, crankcase breather, gasket seal

Question
I have a 14.5 horse briggs engine (model 28n707)(type 0131-01) (code 970314ze) on a toro riding lawn mower. The engine runs perfect but I am getting so much oil back up into the carb, filling my neighborhood with smoke. I just rebuilt the carb included a new needle valve, replaced the crankcase breather, no change.  The oil level is perfect and does not smell like gas.  Compression is 121psi. What else could cause this much oil back into the carb. Could dipstick seal have anything to do with it?  I'm stuck. Any help or ideas would be greatly appreciated.

Answer
Are you using SAE-30 oil?  Does the engine burn oil.  I'm guessing it does as you say there is white smoke.  Have you ever had the valves checked?  Maybe the intake valve needs to be cleaned and adjusted.

I would recommend replacing the dipstick o-ring.  About that time Briggs had some o-rings that were not seailing causing low crankcase vacuum leading to oil burning.

O-ring part number:691870
Dipstick seal part number: 281370

If the correct SAE-30 oil and the dipstick o-ring and seal do not help you need to check the crankcase vacuum and also perform a leak down test to see if there is excessive blow-by in the crankcase.  Vacuum loss can be caused by a leaking  gasket/seal.  Blow-by can be caused by worn internal parts such as valves or rings.

Let me know if this helps.
Eric