Note how much power your Stihl BG 55 Handheld Blower produces when you operate it at full throttle. If the engine gradually loses power once it gets hot, the spark plug may be fouled with carbon or badly worn.
Grasp the ignition wire boot and carefully twist or gently pull the ignition wire off of the spark plug. This will give you complete access to the spark plug.
Assemble the ratchet and socket. Slide the socket onto the spark plug and loosen it using a counterclockwise turning motion.
Check the sparking element on the base of the spark plug. If it is fouled with carbon and engine deposits, clean it with your brass bristle brush.
Examine the sparking element for indications of significant wear. Stihl recommends replacing the spark plug after 100 hours of operation, or at least once annually.
Reinstall the spark plug you've cleaned or install the new replacement plug. Reattach the ignition wire boot to the top electrode on the plug.
Squeeze the retaining tabs on the air filter cover together. When the cover is loose, swing it to one side. This will give you access to the air filter element.
Spray the area around the filter element with compressed air to remove any accumulated dirt or dust.
Remove the filter by carefully pulling it out of the base of the filter housing.
Examine the filter element. If it is badly clogged with bits of debris, use compressed air to blow away the dirt. If the unit is severly encrusted or appears to be damaged, acquire a new filter element from your Stihl dealer and install it in the blower.
Remove the fuel tank cap and observe the condition of the fuel. If it has been several months since you last operated your blower, the gasoline may have deteriorated or become contaminated with moisture. Empty the fuel tank and refill it.
Note the power output of your blower when you operate it. If the performance appears to be sluggish, you might have mistakenly purchased 87-octane gasoline instead of the 89 or higher octane gasoline Stihl recommends. Empty the fuel tank and replenish it with the correct type of gasoline and 2-stroke engine oil blend.
Check the condition of the fuel pickup body. If it appears to be clogged with deposits or has not been replaced in a year, Stihl recommends installing a replacement unit. Purchase a new one from your Stihl dealer and install it.