The Engine

• Perhaps it is best to start at the base of the engine. The engine block is held together by a circular crankshaft, which runs through both halves of the engine, and is responsible for moving the movable parts. Above the crankshaft are the cylinder and the piston, which move up and down, drawing fuel into the carburetor. In front of the cylinder you will see the muffler and the exhaust port to the piston.
  
  

The Fuel System

• The fuel system delivers an adequate supply of fuel throughout the engine. The system begins with the tank. The suction hose inside the tank draws fuel into the carburetor. From the carburetor the fuel flows into the cylinder where it is ignited by the spark from the spark plug. As it ignites, it gives the power to keep the piston pumping up and down. Excess fuel is purged out of the chamber, back into the carburetor and back down to the tank via a purge hose.
  
  

The Ignition System

• The ignition system allows the trimmer to start and ignite the fuel in the chamber. It starts with the rope, which attaches to a pulley and a recoil spring. This pulley attaches to the flywheel, and, when it spins at a certain speed, the flywheel magnet triggers the ignition module to the left of the flywheel. The ignition module sends that current up through HT lead wire, which is attached to the spark plug. The spark plug then fires its spark off into the piston's chamber.
  
  

The Drive System

• When the crankcase and crankshaft start moving, once the piston works up enough power, they will start to spin the clutch assembly. The drive system connects to the crankcase via the clutch. The trigger on the throttle connects to the carburetor, so, when you squeeze it, you bring more fuel to the engine, which speeds up the piston and then the crankcase. When the clutch assembly activates, it powers and spins the head.
  
  

The Shaft and Head

• A long wire runs through the length of the hollow metal shaft, which connects to the movable head. When all of the actions have been completed in the engine, the signal comes down to spin the head. Inside the head are the spring and spool, which house and release more string when needed.