If it has run well in the past and this is a new problem, my first guess with the limited information provided is debris in the carb. Filtering fuel on a gasser is very important. Othe options would be a bad ignition battery, ignition timing being off, both advanced and retarded will cause the engine to overheat. No mention on fuel/oil mix but this engine requires 30:1 air cooled 2 stroke oil. Bottom line is that you really need to be specific to get accurate advise.