While you wait for answers, we may have found some information which could help you.
Click here for Valve Briggs StrattonMy Briggs & Stratton 10.5 engine will start but dies after about 15 mins?
McCulloch lawnmower parts removal ?
Adding oil to mower ?
Petrol or diesel?
Briggs and Stratton SP470?
my briggs and stratton 3.5hp starts up then cuts out straight away?