The fuel filter might be clogged. A clogged fuel filter is often caused by leaving fuel in the edger for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the fuel filter and cause the engine to run roughly. If old fuel was left in the chainsaw, drain the old fuel from the fuel tank and replace the fuel filter.
Highly Likely
02 - Spark Plug
The spark plug ignites the fuel and air mixture in the engine's cylinder to power the engine. If the spark plug is defective, the engine may run roughly. To determine if the spark plug is defective, remove the spark plug and inspect it. If the porcelain insulator is cracked, an electrode has been burned away or damaged, or there is heavy carbon buildup at the electrode, replace the spark plug. Alternatively, if the spark plug hasn’t been replaced in a few seasons, replace it.