Smart Choke on KT725 Kohler

Smart Choke pretty slick and simple, works good, does not last a long time! The bimetal thermostat spring that keeps the choke open after warm up slips out of its little forked linkage and the engine won't idle long before the governor hunting kills it. The vibration dislodges the spring from the fork link. Any permanent fix?
Wrong again! Disassembled smart choke today and all is well! Proper engagement of bimetal spring. Surges on any throttle setting except wide open. No change with or without air filter, choke wide open and steady, governor surging. Only fuel/carb left. Anyone?