hey i have an 82 xr80 and i have replaced the plug, fuel filter, coil, and oil, cleaned out carb, and adjusted the valves. when its cold its hard to start it up but once its going its great. but once it gets hot ( after riding around for about 20 mins or so) it starts bogging out and the motor is basically pulsing. then if it idles it dies and wont start for quite a while. does anyone have any ideas?