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.

Could the engine have flooded? Sometimes after sitting for an extended period, the fuel line may deteriorate and a small "chunk" could work its way into the carb needle & seat and prevent it from closing. DO check for spark. IF none, make sure the seat switch connector is fully plugged in. You might also try manually moving the seat switch to see if it's hanging up or feels "crunchy" inside. I don't have a schematic, so this is off the top of my head.

You guys just saved me a crapload of time and money. I’ve been struggling to figure out the problem for almost a month now. I had been working on a surging engine - cleaned the carb, replaced the fuel filter, drained the gas and added new stuff (only filled 1/4 tank since it wasn’t running 100% yet) - and then suddenly it decided to start konking out after about 20 minutes of run time and whenever it attempted an incline. Thought maybe it was a “too rich” issue but changing that didn't work. But earler tonight i decided to fill the tank and voila, no issues at all. I had changed out the fuel filter to a generic one not thinking it would make a difference. I’m going to switch back to the (correct) Kohler filter and hope to gawd this works. Was almost tempted to junk the whole thing...it was a major sigh of relief to find this post. Thank you!!!!

This is great. Thanks everyone. I will look into adding a fuel shut off valve. I've been reading up on this issue and it seems this is a fairly common occurrence for my engine (13hp Kohler Command). When adding the shutoff valve should I place it between the fuel tank and fuel filter or between the fuel filter and carb? The first being my preferred method since it can be useful when swapping out an old fuel filter. In regards to the carb itself what is typically required here? A good cleaning or is there a something in the carb that needs to be replaced (float needle, gaskets, etc.) I can't say I'm very familiar with carb rebuilds but a number of youtube videos walk through the process very simply. Any guidance here is greatly appreciated! THANK YOU AGAIN!