Troubleshooting a McCulloch chain saw is much like troubleshooting any other chain saw -- they all have common elements which vary only in details. A chain saw is a gasoline-powered engine which drives a sprocket which drives a chain around a long bar. It the engine has fuel, air and spark, it should run. However, if it doesn't start or run smoothly, there are basic things to check before you head to the repair shop.
Start with the basics. Make sure the McCulloch chain saw has fresh fuel, at least half a tank.Test the chain brake, in front of the saw's top handle, to be sure it is not engaged to lock the chain. Test the chain to see that it moves freely, is not binding in the bar and is properly adjusted for tension; a bar that is binding or is too loose or too tight will interfere with saw operation.
Check the air filter on top of the saw; clean it or replace it if it is dirty. Then check the spark plug to make sure it is not fouled; clean or replace it. Examine the spark arrestor screen in the muffler; clean it with a wire brush or replace it. You can adjust the carburetor slightly using the idle adjustment screw, marked T, near the pull rope. Turn it clockwise to increase idle speed, counterclockwise to decrease; at perfect idle, the engine will run smoothly but the chain will not move. If the chain moves, slow the idle.
Try these troubleshooting tips for other problems. If the engine has fuel and good spark and still won't start or dies, check for a bad fuel line or clogged filter; replace as needed. If engine with a good air filter, spark plug and idle adjustment won't idle properly, dies under a load or lacks power, the carburetor may need repair; this is a job for a professional. If the engine smokes, the fuel has too much oil; empty the tank and replace with a proper gasoline/oil mixture. If the chain can't be made to stop running at idle, the clutch needs adjustment; this is another job for a professional.