Small Engines (Lawn Mowers, etc.): Kohler CV409S Gas Lock, fuel starvation, spec numbers

Question
QUESTION: Hello,

My Craftsman tractor has the Kohler CV409S engine.  After an hour , or so, of running, the engine dies from lack of fuel.  The fuel tank is full, there are no obstructions in the tank, fuel line, or fuel filter.  After 2 to 3 minutes, I can see fuel start to flow and fill the fuel filter.  The engine will run for a while and then it is starved for fuel again.  If I disconnect the fuel line from the carb, fuel will flow.  Could the carb need cleaning?  I use this tractor year around (snow plowing).

ANSWER: Watching those clear fuel filters can make you jump to conclusions,
which may or may not be correct.
If it is a fuel starvation issue, then the fuel cap may not be venting, and causing a vacuum to build.
You can test this by loosening the cap when it starts to die.

Otherwise, I would take a new plug and a can of carb spray while mowing, then when it dies, plug on the good plug, and ground it and crank the engine and look for spark, then take off the air filter and give a squirt ofcarb spray and try to start.  If it is
fuel related, it will start on the spray, and you can keep it going by adding squirts, then you will know for sure it is a carb/fuel problem.  Check these things out, and also get all of the model and
spec numbers off of the little tag on the engine.
  Thanks

---------- FOLLOW-UP ----------

QUESTION: Kohler      17.5 H.P.
Family      4KHXS.4902GB
Disp        490
Model       CV490s
Spec        27532
Build Date  4/24/2004

There is no problem with the tank cap vent.  There is spark, and it does fire.

It seems that this problem happens when the air temperature is hot.  

I am going to spray carb cleaner in all the passages.  I will first try this without tearing down the carb.  

Is there an atmospheric vent in the carb?  I am wondering if this might get plugged as the air temp increases.

Thank you for any further assistance.

Steve

Answer
When it dies, you need to confirm if it is a fuel problem, the vapor
lock theory is generally mis-diagnosing the problem.

Looking at the engine's blowups, i don't see a fuel pump, so I assume the tank is above the engine.

Take along the carb cleaner with you, and when and if it dies, try choking it before it dies, and see if it helps.
Then hop off, remove the air filter, and squirt it into the carb
and start again, and if it starts right up, then dies, but can be kept running with light squirts, then you know it is a fuel problem.

If so, it might just be some water in the bottom of the carb.

Try this some, and let me know.