Take a piece of cloth cut in 8" diameter circle, remove the fuel tank cap and replace with cloth held on with rubber band. If motor then works fine for long periods you may then want to get a new OE gas cap. Have had this problem on mowers and cars way back into the 70s. Usually a blocked fuel line issue. Most recently last summer with a Broadmoor. Run great for variable short periods then die, however disconnect fuel line from pump input nipple and gas would come out of line, and remove fuel line on output side of pump and get a gusher. Watched a youtube video from "individualized repair" guy showed a zero turn with same problem, gas oozes thru the blockage which makes mower seem to be working fine until a consistent high demand like spinning blades and operational speed has been put on it. So pulled my tank out, more than a little work,and discovered a small piece of paper coiled into a cone like form stuck in the end of the little fuel inlet to gas line, and a dead bug.