Fuel

• Before you make any adjustments, the Weed Eater must first have a fresh supply of clean gasoline. Fuel that has been sitting in the tank for longer than 72 hours will make carburetor adjustments wrong, and when new fuel gets put in, the adjustment can damage the engine. The oil in the mixed gas will start separating and will cause these incorrect adjustments. Dump out any old or bad gas that's been in the tank for awhile. Always fill the tank with freshly mixed fuel at a 40-to-1 ratio of regular unleaded gasoline to two-cycle, air-cooled trimmer oil.
  
  

Air Filter

• The air filter also needs to be cleaned and washed thoroughly before you can adjust the carburetor. For the same reason as the gas, if the air filter is dirty when the carburetor is adjusted, when the filter gets cleaned the adjustment will be wrong. Take the air filter out of the box and wash it with dish detergent and warm water. Rinse it out under cool water and make sure it's thoroughly dry before reusing it.
  
  

Small Screwdriver

• To make the adjustments to the carburetor screws you'll need a small screwdriver. The carburetor screws are much smaller than the regular screws on the engine, so to turn them properly, without stripping them, you'll need a special screwdriver. Also, some limiter caps may make a screwdriver unfeasible due to the type of cap. If the cap prevents a screwdriver from turning it, needle-nosed pliers will work better--just don't break off the limiter caps.
  
  

Tachometer

• If you're going to make any serious adjustments to the carburetor, beyond what is recommended by Weed Eater, you'll need a tachometer. A tachometer measures the rpms of the engine. This tool will help you accurately set the idle, low and high speeds. It is also what a professional would use if the Weed Eater were brought into a shop. Besides the tachometer, you'll also need the recommended engine speeds at idle, low and high speeds. These speeds vary with every model and can't be found in an operator's manual; you'll need to contact the manufacturer directly.