• 20 parts
  • Checked September 2026

Parts of a Motorcycle Engine

A single-cylinder motorcycle engine cut open from the side, then cut open across.

Parts of a Motorcycle Engine

Name Date

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
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Write the name of each numbered part.Answer key

  1. Camshaft
  2. Rocker arm
  3. Exhaust valve
  4. Intake valve
  5. Valve spring
  6. Cylinder head
  7. Cylinder
  8. Cooling fins
  9. Piston
  10. Piston rings
  11. Connecting rod
  12. Crankcase
  13. Carburetor
  14. Exhaust pipe
  15. Crankshaft
  16. Cam chain
  17. Spark plug
  18. Clutch
  19. Transmission
  20. Drive sprocket

Drawn for this site on 2026-09-30 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the piston and connecting rod up close

All 20 parts on the diagram

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Head, valves, fuel and spark 10

  1. Camshaft A shaft with lobes that open the valves as it turns. On this engine it sits in the cylinder head, which makes it an overhead camshaft.
  2. Rocker arm A lever that the camshaft pushes on one end. Its other end then pushes a valve open.
  3. Exhaust valve It opens to let burned gases leave the cylinder.
  4. Intake valve It opens to let the air and fuel mixture into the cylinder.
  5. Valve spring It pulls the valve shut again after the camshaft has opened it.
  6. Cylinder head It sits on top of the cylinder. It holds the valves and the spark plug.
  7. Carburetor It mixes fuel with the air going into the engine. Many newer motorcycles use fuel injection in its place.
  8. Exhaust pipe It carries the burned gases away from the cylinder head.
  9. Cam chain A chain from crankshaft up to camshaft. It turns the camshaft in time with the piston. Also called a timing chain.
  10. Spark plug Its spark sets the mixture in the cylinder alight.

Cylinder, piston and crank 7

  1. Cylinder The piston moves up and down inside it.
  2. Cooling fins Air flowing past them carries the engine's heat away. The air flows as the motorcycle moves.
  3. Piston The burning mixture pushes it down the cylinder.
  4. Piston rings They seal the piston against the cylinder wall. They sit in grooves around it.
  5. Connecting rod It joins the piston to the crankshaft.
  6. Crankcase The housing around the crankshaft. On most motorcycles the same case also holds the transmission.
  7. Crankshaft It turns the up-and-down motion of the piston into rotation.

Clutch and gears 3

  1. Clutch It connects the engine to the transmission. It lets the rider disconnect them to change gear.
  2. Transmission Pairs of gears on two shafts. Each pair is one gear ratio. Also called the gearbox.
  3. Drive sprocket The small sprocket on the transmission's output shaft. It pulls the drive chain that turns the rear wheel.

How this list was compiled: Every name checked on 2026-09-30 and kept only where two independent sources use it. (1) Wikipedia, text only: Motorcycle engine, https://en.wikipedia.org/wiki/Motorcycle_engine ; Single-cylinder engine; Overhead camshaft engine; Cylinder head; Poppet valve; Crankcase. (2) Honda, CRF250R Owner's Manual, https://archive.org/details/manualzilla-id-6037856 . (3) Yamaha, YZ250F Parts Catalogue, https://archive.org/details/manualzz-id-734353 . (4) US Army TM 9-8000, https://archive.org/details/tm-9-8000-principles-of-automotive-vehicles-1985 . (5) Comprehensive Small Engine Repair (1977), ERIC ED146392, https://archive.org/details/ERIC_ED146392 . Cam chain, clutch, transmission and drive sprocket rest on the two motorcycle makers and Wikipedia; cooling fins on sources 1, 4 and 5, since both makers' engines are liquid-cooled. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's product, nothing traced. Licence: own work

How it works

The engine drawn has one cylinder, air cooling and an overhead camshaft, with the gearbox in the same case. The first view is cut from the side, the second across.

Read the full guide

From the spark to the crankshaft

The carburetor mixes fuel and air, and the intake valve lets the mixture into the cylinder. The spark plug lights it. The piston is pushed down, and the connecting rod turns the crankshaft. The exhaust valve then lets the burned gases out to the exhaust pipe. The camshaft, turned by the cam chain, opens each valve through a rocker arm, and a valve spring shuts it.

From the crankshaft to the chain

A gear on the crankshaft turns the clutch. The clutch passes the drive to the transmission, and the drive sprocket on the transmission's lower shaft pulls the chain to the rear wheel.

  • Engine and gearbox in one case is called unit construction.
  • The second view spreads the shafts apart so each gear shows.

Questions and answers

What are the main parts of a motorcycle engine?

The cylinder head with its camshaft, valves and spark plug; the cylinder and piston; the connecting rod and crankshaft in the crankcase; and, in the same case on most motorcycles, the clutch and the transmission, which ends at the drive sprocket.

What does the cam chain do in a motorcycle engine?

It runs from the crankshaft up to the camshaft in the cylinder head and turns the camshaft, so the valves open in time with the piston. It is also called a timing chain.

Why does a motorcycle engine have fins?

An air-cooled engine has cooling fins on its cylinder and head. Air flowing past the fins carries heat away. A liquid-cooled engine sends its heat to a radiator instead.

Is the transmission part of a motorcycle engine?

On most motorcycles, yes. The engine and the gearbox share one case, which is called unit construction. Early motorcycles had a separate gearbox driven by a chain from the engine.

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