briggs 18.5 intek is blowing fuel/oil out of the crankcase on the crankcase to intake return like a water hose.
#2
Scrubcadet10
faulty needle and or float in the carburetor, not metering fuel flow into the carb.
repair or replace carburetor
drain and refill crankcase oil and change filter at least twice.
#3
ILENGINE
97% of the time that is the result of a float valve that has not sealed and has allowed the carb to empty the entire contents of the fuel tank into the intake, which some will go into the cylinder and past the rings, but most will drain down the breather tube into the engine block. Will require removing and cleaning the carb and replacing the float valve with a repair kit. Draining the crankcase and refilling with fresh oil, which in some cases will need to be changed a second time.
A needle is needed on the float inside the carburetor. That or the float is heavy with fuel inside of it. After that the oil will need to be drained and left to sit for a few hours to evaporate all the fuel possible inside of the crankcase.
While you are at it, I recommend a manual fuel cutoff valve midway in the fuel line to the carburetor. Use that to prevent future issues. Ethanol fuel is hard on small engine carburetors, so use non-ethanol of you can get it in your area.