The early mikunis were notorious for sluggish performance issues, and leaking into the throat of the carb , causing flooding. Is the choke opening all the way - the thermal wax element choke goes and doesn't open the choke all the way nor does it close all the way, making it hard to start in the cold. If you want it to run, replace it with a weber; I changed Geronimo's back in 1983 and never looked back.