Basic Parts of a Small Engine

If you can find a small engine repair shop that repairs small motors, keep their phone number handy!  A small engine shop repairs low-powered internal combustion engines. These are the types of engines that require independent power sources and are found in machines like generators, lawnmowers, concrete mixers, snowblowers, leaf blowers, hedge trimmers, saws, and more. A small engine repair shop is well-versed in the unique parts of a small engine, how they work, and how to fix brand products by any brand. The following are the parts of a small engine:

The Cylinder

  • Known as “the ‘bore”
  • Has an inner wall called the cylinder wall
  • Fits the piston by a precisely machined diameter. The inner wall is very smooth, allowing the piston and rings to operate smoothly.

The Cylinder Block

  • A fundamental part of all small engines
  • The inner part of the cylinder block houses all parts of a small engine
  • Made of aluminum 
  • Must be cast in a mold to obtain its perfect form for each specific engine’s precise operation
  • Its exterior repels heat through the aluminum alloy fins
  • Some liquid-cooled engines may not have these types of fins on their cylinder blocks
  • A single-cylinder is the type found in most small engines; however, other parts of small engines have many cylinders, and the most common of these are in-line, opposed configurations, and V.

The Blower Housing

  • Sits around the flywheel
  • Its purpose is to direct the wind through the blower housing to cool the engine down

The Flywheel

  • Sits on top of the engine
  • Has a metal cover called the blower housing
  • Operates like a fan
  • Cools the engine
  • The blower housing protects the flywheel and other parts of small engines from exposure or human contact, which could cause injuries.

The Cylinder Head

There is a combustion chamber located in many small engines. Small engines have combustion chambers. The top of the cylinder, known as the cylinder head, has a head gasket bolted to it, which forms it. The spark plug is housed in the cylinder head. There are three common types of cylinder heads:

  • A Side Valve Engine houses both valves on one side of the engine.
  • Intake and exhaust valves sit on opposite sides of the cylinder.
  • The cylinder head houses both valves on the top.

The Pistons

  • Made of casted steel or aluminum material 
  • The cylinder houses the piston
  • The head is the piston top

The piston mounts to a connecting rod by a pin and is fastened in place by retaining clips. There may be one to three rings on a piston. These top rings are used for compression. The bottom ring is known as an oil ring. Only a four-stroke engine contains an oil ring. This ring cannot rotate because a pin inside the ring groove prevents any rotation.

The Connecting Rod

The connecting rod connects the crank to the piston. A wrist pin attaches the piston to the wrist pin and is secured by a clip. There may be one or two connecting rods. The bottom part is removable on two-piece units.

The Head Gasket

Between the cylinder and cylinder head lies the head gasket. This gasket seals the cylinder. The function of the head gasket is to hold pressure inside the combustion chamber. This component must endure high temperatures. No water or coolant can enter the combustion chamber if the engine is liquid-cooled. The head gasket prevents this from happening.

The Crankcase

  • The Crankshaft is the part of the engine that rotates.
  • This part sits inside the crankcase.
  • The crankcase converts up, down, and circular motion of the piston.
  • It has heavy counterweights to balance.
  • It sits at a 90-degree angle to the cylinder.
  • There are three different types of horizontal engines:  cars, some lawn tractors, garden tillers
  • Vertical types of engines include: lawnmowers, outboard marine engines,  augers
  • A multi-positional engine is a chain saw

Bearings (such as ball bearings, roller bearings, needle bearings)

  • Come in many styles and sizes
  • They Support engine parts
  • They are resistant to corrosion and scoring
  • They may or may not require lubrication
  • They have small holes in the exterior to lubricate internal components

The Camshaft

  • Operates the intake and exhaust valves
  • Two-stroke engines do not have a camshaft
  • There is one lobe per valve
  • The camshaft rotates, thus lifting the valves
  • Drive style of gears, chain or belt
  • Operates a push rod

The Valves

  • Valves are made of high-grade steel
  • Valves are located on the cylinder block and seal
  • The intake valve and exhaust valve created better engine airflow
  • The intake valve is larger than the exhaust valve

Valve Spring

  • Keeps valves closed, ensuring a tight sealKeeps pressure on the camshaft
  • Prevents floating of the camshaft


  • Reduces noise
  • Made of metal
  • Bolted or threaded onto the engine

Starters (Electric, Rope Rewind)

  • Turn the engine at a fast speed to start the system
  • Draw fuel into the cylinder
  • Create a spark from the ignition system
  • Found in products like chainsaws, lawnmowers, and weed-eaters
  • Electric starter systems are found in machines like cars, ATVs, marine engines, and lawn tractors 


  • Mixes fuel with air for combustion

Speed Governor in Small Engines (Air Vane, or Mechanical)

  • Governors regulate the speed of the engine
  • Varies the throttle position to keep the engine at specific RPM
  • Increases engine speed
  • Will close the throttle so the engine does not over-rev


  • Converts the output speed of an engine
  • Used in machines like lawn tractors, snow throwers, garden tillers
  • Creates a gear reduction to increase the torque output

Lubrication Systems (splash lubrication, pressurized lubrication)

  • The moving parts of an engine require constant lubrication.

Get help fixing your small engine:

If you reside in or around the areas of Northern Nevada, Reno, Incline Village, Carson City, or other surrounding areas, feel free to reach out to reach out to Greg’s Small Engine for all small engine repairs.

Greg’s Small Engine Service and Repair is committed to providing unparalleled service with professional and quality for all small engine service.