One like that can be a carb or ignition problems. I would #1 check and make sure you have a good blue white spark at all the plug wires tha twill jump a 1/4 inch gap or more.
#2 pull the carb drain plug and make sure you have a good steady flow of gas that will fill a pint jar in under 3 minutes. #3 when was the last time you checked the air cleaner and dumped the water and mud in it.
When you clean a carb you need to have at least 3 thing but 4 is better. A good carb cleaner to soak it in. Compressed air to blow it out. Spray carb cleaner to spray out the passage ways and the most important one is a small piece of wire or as I do a torch tip cleaner tool to poke out all the passageways