Greeting! I have a Briggs 42a707 that is driving me crazy! It is mounted on a lawn tractor. Now the meat of the problem: After running at full RPM (while cutting), after about 30-mins. it acts like it is starving for fuel. Sometimes by pulling the chock out, I can get it running somewhat. But after letting it cool down, I can restart it, runs great at low/high RPM. I've let this thing run at idol for almost an hour, and it will run fine. I've totally cleaned the engine, checked/replaced all filters, flushed fuel system, new gas. checked carb inside and out (floats, needle/seat). It seems like it is vapor locking. My next move is to get a fuel pump repair kit, but I'm on an limited budget. HELP!!! I have lawns to cut, and at this rate, I'd be better off with a push mower.