What Al and Brian said, but have a look at the rubber, between the carb and the cylinder, sometimes they can tear.
A quick way to check for an air leak is to turn the saw on it's side for about 5 seconds and then turn it back up right, do this on both sides. If you hear a difference in the RPMs this is a good indication of a leak.
I would try adjusting the idle screw first, this is the screw that adjust the throttle shaft, and is marked by an LA above it on the rubber on the right side if the saw, or the bottom hole.
Next you can try adjusting the low circuit screw on the carb as Brian said, but do it in small increments an in a 1/8 to 1/4 turn at a time. Once you richen the low side you may have to lean the high side out.
Good luck and let us know what you find.