had this mower several year--does anyone know what operates auto choke? no signs of thermostat thing on exhaust no sign of air vane --- this has always run perfect untill i was shaking wet grass of blades and it stalled and refused to start---i assumed i shook something in carb loose --i bought a new one ---it will start 1st pull if i hold choke or use starter fluid--and will run perfect till its runs out of gas ---i just can't figure out the auto choke--190cc