What are the symptoms and causes of a motorcycle misfiring cylinder?
3 Answers
The symptoms of a motorcycle misfiring cylinder are noticeable body shaking at idle speed. By observing the exhaust pipe outlet, the exhaust gas flow shows obvious intermittency, accompanied by severe shaking of the exhaust pipe. A distinct 'putt-putt' or 'thump-thump' sound can be clearly heard. The causes of a motorcycle misfiring cylinder include a faulty spark plug leading to the misfire, or a damaged fuel injector that either fails to spray fuel or provides poor fuel atomization, resulting in incomplete combustion and cylinder misfire. Repairing a misfiring cylinder depends on identifying the specific fault: Damaged components such as spark plugs, cylinder wires, or ignition coils can easily cause misfiring. The 'ignition cut-off method' can be used to determine which cylinder component is faulty, followed by replacing the damaged part. For clogged fuel injectors or short-circuited/open-circuited injector wiring, a 'fuel cut-off test' can be performed to locate the fault point and carry out the necessary repairs.
The symptoms of a misfiring cylinder on a motorcycle are particularly obvious. When riding, you can feel the engine constantly shaking, accompanied by intermittent popping sounds from the exhaust pipe. The power noticeably weakens, throttle response becomes very sluggish during acceleration, and the tachometer needle jumps irregularly. This situation usually occurs because one of the cylinders has stopped working. The specific causes could be excessive carbon buildup on the spark plug or electrode erosion, leading to insufficient ignition energy; it could also be due to aging or leaking high-voltage coils, preventing the spark from reaching; another possibility is a clogged fuel injector failing to spray fuel or insufficient fuel pump pressure causing inadequate fuel supply. The most troublesome issue is worn piston rings leading to air leakage, preventing the cylinder from building proper pressure. Last time my motorcycle misfired, it was because the rubber boot on the ignition coil cracked, allowing rainwater to seep in. It's best to fix these problems early when discovered, otherwise prolonged misfiring can damage the catalytic converter.
I once encountered a misfiring cylinder during a ride. The engine was shaking so violently that my hands went numb, and the exhaust sounded like coughing. Upon inspection, I found the spark plug in the third cylinder was completely covered in carbon deposits. Common causes of cylinder misfires can be categorized into several types: ignition issues such as failed spark plugs or aging, leaking high-voltage wires; fuel supply problems like clogged fuel injectors or dirty fuel filters; and mechanical failures, such as burnt valves causing air leaks or worn piston rings leading to insufficient cylinder pressure. In fuel-injected vehicles, a faulty crankshaft position sensor might also cause the ECU to misjudge and fail to ignite a specific cylinder. During routine maintenance, it's important to check the color of the spark plugs—they should normally be light brown; if they appear black, they need replacement. If you experience a sudden cylinder misfire while riding, you should reduce the throttle and stop slowly. Continuing to ride forcefully can lead to cylinder wall damage.
