The High needle valve and the Low needle valve will allow more or less gas to enter the carburetor. The idle control is a screw to adjust the low speed (with your hand not on the throttle). If the saw starts OK, let it run for about 2 minutes to warm up. If you have to keep pressing the throttle to keep it going, the Low needle is closed too much..turn it counterclockwise about a 1/4 turn and see if it will run with your hand off the throttle. If it runs fitfully and you see a lot of blue smoke coming from the exhaust, it is too rich and you would turn the Low needling clockwise to reduce the gas being fed to the carburetor. The High needle valve is adjusted while you are pressing the throttle hard. It also would be obvious if the engine slowed down while cutting a log. If this happens, turn the High needle valve out 1/4 turn per time until it has power to cut. If there is a lot of blue smoke and the engine has low power, the High needle valve needs to be turned in.
Bud Tuba, October 2009
