may be a clogged fuel cap vent. With a small stiff copper wire, make sure the cap vent is open and allowing air into the tank as fuel is burned.

Definitely check for clogged fuel cap vent.

Did you recently change the fuel filter? If you did, did you use a Kohler brand filter, part no 25050007S? This is the filter your engine requires; there is another Kohler filter that looks similar, but it is for engines with a fuel pump (which your engine does not have - your's is gravity-feed).

Do NOT used any other filter with this engine. Other manufacturers offer similar filters, but this particular engine is finicky about fuel filters.

Just for "gee whiz," the fuel filter for your Kohler is 75 micron, while the other Kohler filter is about 10 micron. This means that gravity will pull gasoline through the filter, but the 10 micron (I'm saying 10, but maybe that's not the exact figure) has to have a pump to force the gas through.

Just an FYI that I had a similar problem with my JD Scotts 1642 when I replaced the original Kohler filter with the standard John Deere clear filter that is included in their home maitenance kits. The engine would stall out on slight hills once the tank got down to about half full. It took a while to figure it out, but someone suggested replacing the filter with the OEM Kohler and the problem was fixed. The John Deere replacement is too restrictive for these engines.

Thank you!! I'll check the fuel cap. And yes...shame on me, replaced the filter with with a Home Depot special. I'll be back with an update.

If I might offer another suggestion, turn the fuel line shutoff valve to the "off" position whenever you shut your engine down. If you won't be running the engine within the next few days or week, leave the engine running, close the fuel shutoff valve, and let the engine run out of gas. Letting gasoline - particularly if it contains ethanol - in the carb can really gum things up.

have a john deere stx 38 with kohler motor 12.5 hp it only starts if u poor gas in carburetor then stalls like its not getting gas tank is full lines aare clear

Try again , Josh.
With all the mis-spellings and non-editing, your post is not comprehensible.

School teachers aren't allowed to teach! Too many regulations that prevent that. When i went to school, a sharp smack on the back of the head quickly got our attention, and stopped any foolishness in class! Thank God we didn't have any of these new attention getters, way back then, except the ruler, the teachers' hand, or promises of more unliked punishments!
Reading some of the comments in this and other venues makes me wonder if the former "students" didn't have electronic games hidden in a hollowed-out text-book! It has been a long time since i attended grade and high school, but the things they taught are still with me. (86) YOA!

Oh come on you letter to the editor guru's !

Josh : Check your fuel filter and if clear without any restriction , ensure the carb fuel circuits are clear. You can either try concentrated fuel cleaner additives or remove the carb jets and clear the circuits with carb spray and small guage tag wire and compressed air. Ensure to find a fuel stabilizer additive in the future and always use fresh fuel.

Josh, there are any number of things that can cause your problem. A few of the more obvious, and easily-dealt with, problems are:

Carb problem, as addressed by ewalk above.
Dirty, clogged air filter
Clogged fuel filter
Bad spark plug

I suggest that you replace your air filter, then disconnect the fuel line where it attaches to carburetor; if you don't get a flow of fuel, then clean out the gas tank and replace the fuel filter (use ONLY Kohler PN 25050007S - DO NOT use any other filter.) Clean the carb as ewalk suggested. Replace the spark plug (RC12YC), after gauging it to the correct gap (0.040). Get a can of fresh gasoline and add a double shot of Stabil or Seafoam to it. Fill the tank and give it a try; I suspect that these steps will get you back in the saddle again.

If your engine has a fuel shutoff solenoid, let us know. (That is, is there a small unit on the bottom of the carburetor with an electrical wire plugged into it.) IF you have a solenoid (not all STX38 Kohler engines have one) a failure of that could prevent gasoline getting through the carb and into the combustion chamber.

TG: Excellent recommendation on the elect. fuel solenoid valve verification and checkout Some units have a pump and solenoid where others are gravity feed without :)

i know this post is really old but who sells the fuel filter part number Kohler PN 25050007S i can find 2505007s but not 25050007s

Very possible that the 10-yr old post of that number earlier in the thread has an extra zero in it.

One way you can tell is to search online or at Kohler for the manual for your engine, and see what it says is the part number for the filter.