Kohler 24 hp -7000 series -specificationsps-kt-735-3058-serial #4627404504-year 2017

I need heip in trying to stop the engine from SURGING. I was told to put a additive in the gas and that would help.
Did not work. At idling speed the engine revs up then slows down to almost quitting then revs up again. Can anyone
give me instructions on how to fix this problem.

Remove carb, thoroughly clean hoping you don't miss something, install carb repair kit and reassemble,