If you're having trouble starting your chainsaw, or if it's running rough, one of the first things you should check is the L and H settings. These two settings control the amount of fuel and air that reach the engine, and they're usually marked with an L for low and an H for high.
To adjust the L setting, start by turning off the saw and removing the spark plug. Then, use a flat-head screwdriver to turn the low speed adjustment screw clockwise until it stops. Next, pull out the choke lever and turn on the saw. Let it run for a few seconds, then turn it off. Finally, reinstall the spark plug and test-run the saw again.
The H setting is adjusted in a similar way, but you'll need to use a Phillips head screwdriver instead of a flat-head. Start by removing the spark plug and unscrewing the high speed adjustment screw until it's loose. Next, turn on the saw and let it run for a few seconds before turning it off again. Finally, reinstall the spark plug and test-run the saw once more.