What are the symptoms of a dead cylinder?

When a motorcycle cylinders completely fail (commonly known as a "dead cylinder"), the following obvious symptoms will appear:

1. Severe engine vibration, like "coughing"

Symptoms: The motorcycle vibrates like a phone on vibrate mode at idle, and the rearview mirrors become blurry.
The engine feels sluggish during acceleration, jerking and jerking.
Cause: The cylinder is not working, resulting in intermittent power; other cylinders are struggling to keep up.

2. Exhaust sound becomes hoarse, and exhaust emissions are abnormal

Symptoms: The exhaust sound fluctuates in volume, sounding like a hoarse voice.
Black smoke (incomplete fuel burning) or white/blue smoke (oil/coolant leaks from the cylinder).
Cause: Either there is no ignition in the cylinder, or the fuel is burning engine oil/coolant.

3. Severe power loss, sluggish throttle

Symptoms: Twisting the throttle feels like stepping on cotton; the engine speed doesn't increase.
Noticeably weak when climbing hills, even experiencing a drop in speed.
Cause: The faulty cylinder is not contributing power, leaving the engine "depleted."

4. Difficulty Starting or Complete Failure to Start

Symptoms: The engine requires several attempts to start when cold.
The engine suddenly stalls while driving and cannot be restarted.
Causes: Cylinder leak or ignition failure, insufficient compression pressure.

5. Abnormal Noises: Metallic knocking/leaking sounds

Symptoms: A "clicking" sound from the engine (pistons moving around in a faulty cylinder).
A hissing sound (leaking cylinder head gasket or crack).
Causes: Loose internal cylinder parts or failed seals.

6. Abnormal Oil/Coolant Consumption

Symptoms: Oil level drops rapidly, but no leak can be found.
Coolant level drops inexplicably, requiring frequent top-ups in the coolant reservoir.
Causes: Cylinder cracks or failed seals, allowing oil/coolant to enter the combustion chamber and burn.

7. Wet Spark Plugs or Carbon Deposits

Symptoms (check spark plugs): Spark plug electrodes are wet (covered in oil or coolant). The electrodes are heavily carbonized, even burnt and deformed.
Cause: Abnormal combustion in the cylinder, contaminating the spark plugs.