Four-stroke Engines

Question 1

What are the four strokes in a 4-stroke engine?

Answer 1

• intake stroke
• compression stroke
• power stroke
• exhaust stroke

Question 2

What happens in the intake stroke on a 4-stroke engine?

Answer 2

The piston moves down, intake valve is open, fresh afm sucks into the combustion chamber.

Question 3

What happens in the compression stroke on a 4-stroke engine?

Answer 3

The piston moves up, fresh afm is compressed; all valves are closed.

Question 4

What happens in the power stroke on a 4-stroke engine?

Answer 4

The spark plug ignites AFM - burning it - and the explosion pushes the piston down creating torque.

Question 5

What happens on the exhaust stroke on a 4-stroke engine?

Answer 5

The piston is moving up, and the exhaust valve is open which causes the burnt gases to flow/push out.

Question 6

What is the compression ratio on a 4-stroke engine?

Answer 6

10-1

Question 7

Which valve is bigger on a four stroke engine? The exhaust or intake valve?

Answer 7

Intake valve

Question 8

What does the camshaft do?

Answer 8

The camshaft opens the exhaust and intake valves. It has a direct influence on the breathing of the engine.

Question 9

What does the crankshaft do?

Answer 9

The crankshaft connects to the connecting rod which is connected to the piston to move the piston up and down.

Question 10

What do the oil control rings do on a 4-stroke engine?

Answer 10

They help provide lubrication for the compression wall.

Question 11

What do compression rings do?

Answer 11

They help keep pressure about the piston.

Question 12

What do the timing gears do on a 4-stroke?

Answer 12

The timing gears control the timing of the engine; they move engine parts.

Question 13

Which timing gear is smaller? Crank gear or cam gear?

Answer 13

Crank gear