It sounds like the low speed needle on the carburetor needs adjusting. It should be turned counter clockwise to open it slightly. Try 1/8 of a turn and see if that helps. If not go another 1/8 and keep going until the saw will accelerate ok. Before doing the adjusting the saw should be operating temperature which is hard to do if it will only idle. Try starting it and then pull the choke out a bit and pull the throttle trigger , with the help of a bit of choke it should rev up. Once you have it accelerating ok and having richened the low speed needle you will have to adjust the high speed a tiny bit leaner to compensate for this. Again try 1/8 of a turn only at a time.
Hope that helps.
