Try setting the carb back to stock and tune from there. Sounds like the bottom end isnt tuned right. Diffrent temps, humidity, and sea level will change the tuning. As for your pull starter it sounds like the one way bearing is getting oil and gas in it. The heat may be drying some of it up when its warmed up. Take it out and spray it out with brake cleaner and swab a Q tip around inside it to spin the oil off of the bearings. That should help ya out.