All About Chain Saw Motors All About Chain Saw Motors

A household chain saw uses an air-cooled, two-stroke, gasoline-powered engine. This is commonly called the gas chainsaw. Though electric chainsaws have been around for many years, gas models are generally sturdier and more durable. Further, their parts are easily replaceable and can be found in most hardware stores.

Irrespective of their power source, all chainsaw motors have a basic configuration that is easy to understand.

Chain Saw Motor Mechanism: The Basics

  • The standard garden chain saw uses a 16-inch cutting bar. The circulating chain is wrapped around this bar. The chain carries the metallic teeth that give the saw its cutting proficiency.
  • This chain is moved according to the movement of the Centrifugal Clutch. Whenever the engine is switched off, the clutch remains in a disengaged state. When the engine is started and gains momentum, the plates start spinning towards the outside direction, engaging the clutch. This in turn makes the chain to move rapidly.
  • The standard chain saw uses a 49 cc standard engine. The motor consists of a cylinder, connecting rod, piston, carburetor, crankshaft and magneto. The engine develops a power of about 3 to 4 horsepower.
  • The small oil pump along with a chain-oil reservoir, lubricate the chain.
  • The engine is started with a pulling action, tugging at the pull starter.
  • Most contemporary chain saws use an air-cooled engine which removes the additional weight of the water, radiator and water pump.
  • Motors equipped with a two-stroke engine don’t use any valves or cams and are capable of generating more power with every single crankshaft rotation.
  • The tank is able to hold about half a liter of gasoline mixed with the with engine oil of the two-stroke engine.
  • The mixture of gas, oil and air in the carburetor are drawn to the engine through the vacuum-like suction of the crankcase.
  • The exhaust flows through the spark arrestor, eventually directed to the outside.


The role of the carburetor is to approximate the amount of fuel that needs to be mixed with the air seeping into the engine. Carburetors that malfunction, tend to disrupt the entire motor function, releasing a lot of smoke, stall easily and cause fuel wastage. It is made of three main parts:

  • Throttle Plate
  • Venturi
  • Jet


This part is need to create the electrical charge. The charge is needed for firing the spark plug. The spark plug controls the ignition inside the combustion chamber. This mechanism is critical for the appropriate ignition of gasoline inside the motor. The magneto does its jobs by creating a high-voltage surge in accordance with the movement of the crankshaft. It is also called the electrical generator and is regarded as an exact reverse of a standard electromagnet. The important parts of a magneto:

  • Armature
  • Primary coil/Secondary coil
  • Electronic control
  • Pair of strong magnets


This is an aluminum disc containing the blades. When the blades move, they suck-in the air and force it towards the fins of the combustion chamber. This is how the engine is cooled, i.e. moving cooler, external air towards the inside. The flywheel also carries the magnets that are used by the magneto.

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