I have an 04 23hp Kohler Exmark Turf tracer walk behind. When I engage the blades it acts like it's starving for fuel. Filter is clear, plenty of clean gas. I was mowing and noticed that at the end of a row it would fall on it's face again. If I stopped it would rev back out and I was for another minute then it would do it all over again.. Fuel Pump maybe? Carb out of adjustment?