Oil flowing into carburator

I have a riding mower which is a yard machine 13AM675G062. It has a Briggs and Stratton 14.5hp as the motor. It was hard to start, The battery was old and weak so I picked up a new one. When I got home and replaced it it still hardly turn over but it did start and then it died. After looking at it I took the air cleaner off and sprayed some carb cleaner in it and tried to start it again, it started and ran alittle longer then died. I then seen that oil was pouring into the carburator from the air breather(the metal tag that is under the air filter) this happens every time the motor dies it's alot of oil. This is the frist time this has done anything like this. It run fine just the other day when I mowed the yard. I 'm going to try to do a comp check on it and take off the carb and intake to see if a gasket or seal is broke. I'm thinking it maybe the rings but it should have been acting up before this if thats it. Any ideals that you my have let me know what to look at or if something that needs fixed. Thank You Mike