I have seen several Kohler Governors that have broken the internal (plastic) gear. If this has happened to yours, you have a big job ahead of you. If you have limited experience you may find it easier to look for a used engine or even an old tractor that has a good engine. Generally you can "probably" use any engine of similar hp as long as it has the same size crankshaft. Now as far as the governor goes, lots of people play with it to solve problems that actually have NOTHING to do with the governor, surging for instance. Except for a broken or stretched spring there is literally NEVER a legitimate reason to mess with it. I recently worked on a Kohler V-twin where the original owner took apart the throttle/ governor linkage and the installed the bracket upside down, putting it back together properly was a horror show. If you do not have lots of experience with the exact engine model you are working on, use your cell phoneAand take lots of pictures to be certain you are putting it back together properly. Again I stress that there is a 99.5% percent chance that there is never a reason to mess with your governor something else, probably the carb that is causing the problem.