I've got a Kohler command pro 12.5 running rich and surging at the governor, and I can't figure this one out???? I rebuilt the carb, the governor is set @3600 and I got in a new plug in it. Problem is, when its running it does a lot of governor hunting unless it's under a big load, and has a hiccup once in a while. When I check the plug it's black & sooty. I even swapped the carbs off of my command 14 and 15 to try - same deal. Anybody have any ideas?