A lot of these older saws have fuel line problems. I've had quiet a few with leaks in the lines at the top of the tank causing an air leak in the fuel line. To rule out a fuel delivery problem try hooking up a 2ft length of translucent fuel line to the carb. Fill a clean dry soda bottle with fresh mix and put the end of the fuel line in the bottle. Pull her over and check to see if she's pulling fuel into the carb, If it does see how she runs. If she runs well then replace the fuel lines, filter and rebuild the breather in the fuel cap. If you're getting the same results I'd expect an air leak, more than likely a crank seal.