I just had my choke fixed on the carb on my 12.5 kohler....somehow a limb hit the choke and broke a stop off and it was always on choke. Anyways since then it's been missing, but only when the blades are disengaged. When the blades are engaged and you are mowing it runs great. I pulled the carb back off it today and made sure everything was clean. Any ideas what it could be??