Small Engines (Lawn Mowers, etc.): John Deere 160 dies when hot, kawasaki fb460v, electric fuel pump

Question
Hello
I have a John Deere 160 with a Kawasaki FB460V engine.  

Last summer it developed an issue where it would loose power and stall out when hot.  It will start to sputter and if you cut the load to the engine either by pushing the clutch or shutting off the blades it will run with the choke on, but then eventually want to die out.

My dad had someone look at it who replaced either the coil or the ignighter and the fuel pump. no real change.

My dad gave it to me this summer, and so far i've cleaned out the carb, the float appears to be good, changed the fuel filter, and put an electric fuel pump on it(on the asumption that since the engine has never been apart its loosing vacuum)  no changes.

I put an inline spark checker on it and it keeps spark right until the engine stops moving.

a check of the plug looks evenly brown with no oil or gas fouling.

my next thought was to pull the gas tank and clean it and replace the fuel line.  however it appears the fenders need to come off for that?  any sugestions would be helpful.

Thank You  

Answer
  It sounds like you need to adjust the valves, they need to be
set at .004-.006, if they get too tight, the engine will run
until hot, then lose compression.  Check out youtube, there is a guy with some good videos on valve adj. procedures, just search lawn mower valve adjustment.