I have a Toro mower with a Briggs & Stratton engine (model: 312777. Type: 0128E1), OHV 4-cycle, single-cylinder, 17 hp.

I am getting lots of fuel in the crankcase. (float needle issue? )

Also, what is factory compression? I am getting about 65.

Steve

I can almost guaranty it's a bad needle or seat. Drop the bowl and clean or replace the needle. Flush with some gasby raising and lowering the float with the bowl removed. Plug your model in here and maybe you can reach the manual. Buy Parts, Supplies & Accessories - Briggs & Stratton

I have the 14 hp vanguard single with same problem. I just put an fuel shut off valve between the carb and fuel filter. Just shut valve off and let run carb dry.

The rubber tip on the needle valve is wore and needs replaced,That engine has a compression release on it , so 65 means nothing.Shut off isn't fixing anything , it still has a problem .
Luck