If you have verified the saw has good compression, pull the plug, then hold it against the cyl and pull the starter to check for spark. If you don't have spark it's a coil/wiring problem, if you do have spark, squirt some fuel mix into the plug hole, put the plug back in, hold the throttle open and see if it fires. If it fires and dies quickly, probably nothing wrong with the ignition and it's time to look at carb issues such as fuel line integrity, choke operation and correct operation of the internal carb parts.