With so many different parts, a lot of things can wrong with a Ryobi trimmer. When trying to fix a problem on your trimmer, you should start by diagnosing the problem into one of three categories: air, spark or fuel. All of the parts inside the engine work in one of these three areas.
Fuel problems, the most common problem on trimmers and most two-cycle engines, require constant attention to keep them from disrupting your trimmer's function. The mixed fuel inside the gas tank goes bad after 1 to 2 weeks. If you left the gas inside the tank, or even worse, ran the bad gas through the tank, you will start noticing fuel problems.
Fuel problems occur when bad or old gas dries up in the fuel line, carburettor or combustion engine, leaving behind a gummy residue that chokes your engine of fuel. Symptoms include slow or rough starts, poor idling and dropping engine speed under full load.
Problems in your fuel components will also occur through regular use, so it's important to follow the cleaning and maintenance guidelines set forth in your operator's manual. Mixing the gas to the proper fuel-oil ratio will also slow any developing problems. The fuel lines and fuel filter need to be replaced on a seasonal basis at a minimum. Clean the carburettor with a spray on a biweekly or monthly basis depending on how often you use the trimmer.
While not as common, compression, or air flow, problems signal serious damage to the engine. You will notice compression problems when the starter rope is either too hard or too easy to pull out. You may also notice the engine dropping off under load.
Compression problems occur when the engine can't hold the proper pressure, usually around 90 psi for Ryobi trimmers. This usually means an air leak is present on your seals around the crankshaft, piston or a crack in your cylinder. Often these problems require extensive repair, so it may be wise to weigh the cost of repairs against the cost of purchasing a new trimmer.
Before giving up on your trimmer, clean or replace the air filter. Check and clean the spark arrester screen inside your muffler. Inspect the muffler port for any clogs or a backup in the intake and outtake of air and exhaust.
When your trimmer just won't start, the problem usually lies in the spark plug or ignition system. If you've cleaned the fuel tank, replaced the fuel line and cleaned the air filter and exhaust system, it's time to check for a spark.
You can determine if a spark is present by disconnecting the spark plug from the engine. Hold the rubber spark plug terminal, with the spark plug inside, near a metal point on the engine. When you pull the starter rope, can you see a blue spark across the points? If not, replace your spark plug and try again. If there's still no spark your ignition system is likely wearing out and will need to be replaced soon. If the spark is a weak yellow, clean the rubber terminal and look for damage in the wires leading to the ignition switch.