Small Engines (Lawn Mowers, etc.): Fuel issue with Sears Tractor, FUEL FLOW CONDITION

Question
I have a Sears lawn tractor 917.273140 with a 17HP Kholer engine (CV490, type 27508).  The gas doesn't flow into the carburetor very well.  If I take the hose off at the carburetor, it will free flow out the end of the tube.  But once it is attached to the carburetor, it barely runs to the carburetor.  I can see it barely running thru the fuel filter on the way to the carburetor.  The engine runs OK as log as I keep the gas tank full.  But if it gets more than 2/3 to 1/2 empty, the engine will die, especially if I'm going up hill.  Any help will be appreciated.

Answer
Hi Bob,

Okay, you have clearly outlined the symptoms with your machine.  In order to clarify this situation though; you mentioned that the fuel was freely running from the gas line leading from the tank, (when disconnected), but then the fuel doesn't flow properly after connected to the carburetor.  Which diagnostics helped you to determine this?

Engine IN A NO-START CONDITION is troubleshooting is done as follows:

1.  If engine isn't starting CHECK FOR SPARK.
2.  THEN inspect spark plugs to see if they are WET or DRY.

IF WET

a. Defective Spark Plug.
b. Air filter dirty.
c. Fuel too old (not fresh)
d. Flywheel problem
e.  Carburetion problems (after flooding or too much priming)
f.  Ignintion problem

DRY

G. Inspect fuel supply as well as Fuel cap vent (fuel cap must be in good condition to allow air to escape)
H.  Fuel system obstruction (check filter +/or screen not dirty)
I.  Carburetion problem
J.  Poor compression
you can use a spark plug tester to test for spark.  Look closely at spark plug for wet condition.  This would mean the gas is getting to the cylinder.  (Try injecting a teaspoon of fuel directly into the cylinder [through the spark plug hole] to see if it starts).  If it does start then the fuel must be restricted somewhere (but where?).

If the spark is dry, check your fuel system before arriving at the carburetor. Remove the air cleaner assembly and inspect the choke shutter making sure it completely closes.  Check if fuel comes out of the main nozzle during priming.  If you note a normal amount of fuel during priming, then consider removing the carburetor for servicing.  

If you determine that there isn't a normal fuel flow then this points to >FUEL, or >FUEL LINE,> FILTER,> & /OR TANK NEED CLEANING OR MAINTENANCE.

Check engine compression. If you notice the compression is too low, the spark dry with regular fuel flow and a normal functioning carburetor, then an internal engine problem exists.  

A wet spark points to fuel being supplied by the carb.  Engine might be hampered by clogged air filter. Also this could point to a spark plug which is carbon shorted or other spark plug problem (need replacement), too much choking or over-priming, poorly adjusted or defective carburetor, or ignition timing that is off.

Note: Using gas with a 77 Octane or higher is recommended.  
     Small engines run at low compression ratios SO THERE'S NO GAIN WITH ANY HIGHER (THAN 77) Octane Gas.   

I HOPE THAT YOU FIND THIS INFO HELPFUL AND HOPE THAT YOU GET YOUR MACHINE UP AND RUNNING SOON.  LET ME KNOW.

HOWARD