Auto choke still working? If you see thick, brown grease on the end of the wax pellet actuator rod, it's dead. Other than that, check for the usual vacuum leaks. And the not so usual (like the diaphragm in the auto choke release assist - they do perish and fail and I have replaced a couple when meddling with the Mikuni) Also check the fuel cut solenoid on the side of the carb (if it doesn't kick when you unplug it and plug it back in with the ignition on, it has issues) and possible fuel blockages/dirty jets etc.