When the trigger is pressed and the throttle is increased on a backpack blower, a metal wire pulls open a vent on the carburetor, allowing more fuel into the passages. The increase in fuel translates into an increase in engine speed. If the throttle is stalling, a problem is occurring in the fuel delivery system and an insufficient amount of fuel is reaching the carburetor to power the engine. This problem often occurs in conjunction with the use of bad, old or poorly mixed gas.
Unscrew the cap on the backpack blower's fuel tank. Drain any gas that was mixed more than one week ago from the fuel tank into the approved fuel container. Scrub the walls of the tank with the brush and rag.
Pull the pickup nozzle and attached fuel up into the tank opening with the metal hook. Pull the pickup nozzle off the end of the fuel line. Replace the pickup nozzle if it's dirty or the screen is clogged. Insert the new pickup nozzle into the end of the fuel line. Set them back into the bottom of the fuel tank.
Unscrew or unhook the air filter cover. Pull the air filter pad from the filter box. Wash the air filter in water soapy with dish detergent. Rinse it under cool water and give it one night to dry thoroughly. Reinstall the air filter and cover to the engine.
Mix a fresh batch of blower fuel. Pour the two-stroke engine oil and regular unleaded gasoline into the approved fuel container. Combine them using the mix ratio provided with your model's fuel specifications. Shake the gas and oil for one minute before putting it into the fuel tank.
Start the backpack blower's engine and allow it to warm up for at least 10 minutes. Find the three carburetor adjusting screws on the side of the carburetor. Insert a small screwdriver onto the idle speed screw, which is often set apart from the high- and low-speed screws.
Rotate the idle speed screw clockwise until the blower starts blowing on its own. Turn the idle speed counterclockwise again until the blower stops. Rotate the screw clockwise again to the highest engine speed before the blower starts working.
Insert the small screwdriver onto the low-speed adjusting screw, often marked with an "L." Turn the screwdriver clockwise until the engine produces a higher-pitched surging sound. Stop turning the screw and move it counterclockwise until you hear a bubbling sound from the engine.
Move the low-speed screw between these two extremes to find the cleanest, smoothest engine sound. Fine-tune until the engine sounds its best. Depress the trigger and check the acceleration of the engine. Increase the low-speed screw 1/8 turn clockwise if it's still sluggish. Readjust the idle speed in the same manner once the low speed is set.