I have about 30 hrs on my Kohler. After cutting a yard I drop it to low speed to cool down on the trailer while I lock it down about 30 seconds or so. When I fire it back up at the next yard it gets stuck In choke mode. I can raise the throttle and it still says in choke mode. It also puffs out the excess gas. I have to take of the breather and tap the butterfly to get it out of choke. Any idea what's causing this.