While you wait for answers, we may have found some information which could help you.
Click here for Cannot Briggs Stratton EngineMy Briggs & Stratton 10.5 engine will start but dies after about 15 mins?
McCulloch lawnmower parts removal ?
Adding oil to mower ?
How can I fix Mountfield Laser Omega 46 Lawnmower?
lawn mower briggs and stratton classic 35?
Petrol or diesel?