My unit will falter after running 15 minutes
I have a craftsman yard tractor, model #917.273351 with a briggs & stratton engine, model #31C7070230e1. After running for 15 minutes while mowing, it acts like starving for fuel & attempts to shut down. I will then disengage blades & drop throttle to idle & it will stay running, but throttle up & same thing occurs. I have changed air filters, spark plug & fuel filter. Today I sprayed carburetor cleaner into carburetor to clean, but still same results.