I HAD THE SAME PROBLEM WITH MY 6.5 H.P. BRIGGS & STRATTON LAWNMOWER ENGINE. AFTER CHECKING TO MAKE SURE THE CARBURATOR IS CLEAN, AND THAT THE GAS AND AIR FILTER ARE CLEAN.

IF THIS DOESNÂT WORK CHECK TO SEE IF THE COIL IS CUTTING OUT WHEN IT GETS HOT AFTER RUNNING FOR LESS THAN 30 SECONDS. TO DO THIS TAKE A SPARE SPARK PLUG AND GROUND IT TO THE ENGINE BLOCK, START THE ENGINE AND WHEN IT STOPS TAKE THE ING. WIRE OFF THE PLUG AND TRY IT ON THE SPARE PLUG, IF YOU SEE A SPARK WITHIN 30 SECONDS THE COIL IS GOOD. I FOUND MY PROBLEM TO BE A BAD AUTOMATIC CHOKE, NOT WANTING TO BUY A NEW CARBURATOR FOR SUCH A OLD LAWNMOWER, I FOUND THAT I COULD KEEP THE ENGINE RUNNING BY RESTRICTING THE AMOUNT OF AIR ENTERING THE AIR INTAKE BY HOLDING MY FINGERS OVER THE AIR INTAKE HOLE, SO I CUT A SMALL PIECE A WOOD AND GLUED TO HOLE IN THE AIR INTAKE. PUT THE AIR FILTER BACK ON AND CUT MY LAWN.