The carburetor in a Husqvarna chainsaw controls the amount of fuel and air flowing into the combustion chamber. It allows the chainsaw to operate efficiently at different speeds, pulling fuel into and out of the engine. Without a properly working carburetor the chainsaw will perform poorly and may not even start at all. Dirty carburetors cause a majority of all problems on Husqvarna chainsaws, so they need regular cleaning and attention, every season if the chainsaw gets used weekly.
Refit the throttle and choke butterflies to the carburetor if your Husqvarna chainsaw uses them (not all models do) and if they were removed during disassembly.
Refit the high and low speed screws to the top of the carburetor. Put their springs into their holes, and then press down the screws gently. Don't tighten these screws as it will damage them.
Place the fuel filter onto the tip of the small screwdriver. Press the fuel filter into place on the top of the carburetor. Set down the pump diaphragm, gasket and pump cover on top of the fuel filter, topside of the carburetor. Tighten the retaining screw with the screwdriver.
Fit the needle valve into place, on the bottom side of the carburetor. Connect the needle valve's lever arm to the spindle. Press the spring into the hole beside the needle valve gently. Set the lever arm and spindle onto the needle valve and spring. Tighten the screw to hold them in place.
Set the ruler on top of the lever arm to make sure it is level with the cover face. Press the lever arm down gently if it sticks up a little. Replace the lever arm if it is bent too badly.
Refit the metering diaphragm, gasket and cover to the bottom side of the carburetor. Tighten down the screw to hold them in place. Reinstall the carburetor into the Husqvarna chainsaw.