re: Kohler Engine Issue

Does the surging occur even if there's no load on it the engine? If not, the high speed jet is partially blocked and you need to clean the carb.
Another way you can check to see if it's fuel related is to rev it up to where the problem starts occurring and add some supplemental fuel into the carb via starting fluid or propane. If the problem clears up, it's most likely fuel related. It could also be a vacuum leak too but that's not very common.