Hi all, I asked this question last year and still was not really able to piece together an answer. I have a 3 year old 16 HP B&S OHV model 286H77 on my Toro Zero-Turn mower that last year would stall out after maybe 15 minutes or so of summer-temperature lawn mowing. Seems as though when the engine temp gets higher it wants to quit. So I went out to the garage last week while still in the 50 degree temp range around here and gave her an oil/filter change, checked the plug (it's new), put fresh gas in it and fired it right up. I got up to operating temperature, then did a test run for a good 20-30 minutes under load (blades spinning and driving). It did cough occasionally but recovered and I am not sure but the power seems just a little less than I expected. The replies to all of my posts suggested I look at valves, etc. , but I'd rather not get that deep yet. My local repair guy said that for a machine with only around 200 hours that he does not think the problem is that in-depth. I have disassembled and cleaned carb, checked the gas cap for venting, changed the fuel filter, have fresh gas, I am running out of ideas and time. I'm looking for any simpler ideas on what to look for. And no disrespect to those that have replied with their input in the past.