While you wait for answers, we may have found some information which could help you.
Click here for Briggs Stratton ClassicBriggs and Stratton SP470?
lawn mower engine hunting?
my briggs and stratton 3.5hp starts up then cuts out straight away?
lawn mower won't start?
lawn mower briggs and stratton classic 35?
My Briggs & Stratton 10.5 engine will start but dies after about 15 mins?