While you had it open, did you check the tab on the governor shaft? Make sure it's not missing and should be over the shaft in the governor gear assembly. Follow the instructions for adjusting the governor in the Kohler service manual. Make sure the throttle linkage/cable are operating and adjusted correctly. On my 76-444 I just bought, I noticed if I start it at full throttle, the engine will race like crazy for a second or two, then settle down. I found when cold, about half throttle, get it cranking over, add some choke it will fire right up and run good. No racing. Choke goes off as soon as it fires. Warm starts are the same but no throttle. Will start warm with a small amount of throttle and no choke also. Check butterfly in carb to make sure it operates freely too.