Pictures would be helpful, I've never seen a Kohler engine on a pressure washer. Lately, however, they have sourced engines from so many sources that anything is possible. The easiest way to troubleshoot this is to remove the air filter and administer a little fuel (gas) to the air intake. If it responds, you have a fuel (or lack of) problem. Next, how does the compression feel when you pull it over? Most small engines can't be tested with a compression tester, as they have compression release devices on the camshaft. Checking the valve clearance would be my next step.