What to Do About Abnormal Noise from a Motorcycle Crankshaft?
4 Answers
Motorcycle crankshaft abnormal noise requires repair or replacement. Abnormal noise from a motorcycle crankshaft can affect the engine: The crankshaft is a key component of the engine and a direct participant in the operation and power transmission of the entire engine. If abnormal noise occurs, it indicates excessive clearance in the internal needle bearings. If not repaired promptly, the engine may be completely ruined. Definition of a motorcycle crankshaft: A motorcycle crankshaft mainly consists of connecting rods, cranks, and bearings, making it an assembled component rather than a single piece. As an assembled part, it is prone to developing excessive clearance during normal engine operation.
After riding motorcycles for so many years, my experience tells me that crankshaft noise never means anything good. This component is inside the engine, and if it starts making clicking or clunking sounds, there's an 80% chance it's due to severe bearing wear or a loose big end of the connecting rod. My old bike was exactly like this - it started with slight noise at idle, which I ignored, but the sound kept getting worse until it finally seized up on the road. Check the oil pump pressure immediately and disassemble the engine to inspect for crankshaft axial play. If the bearing wear exceeds 0.15mm, it needs replacement. Remember, never push your luck - otherwise you risk cylinder scoring or complete engine seizure, which would be a much bigger loss.
When it comes to crankshaft noise, it depends on the specific situation. For new cars, it might be an assembly issue, while for older cars, it's usually due to wear and tear. Try listening for changes in sound when you rev the throttle: if the noise gets worse with higher RPMs, it's likely excessive clearance in the connecting rod bearings; if it's noisy when cold but quiets down when warm, it could be the wrong oil viscosity or a clogged oil passage. Last time I encountered this, I switched to a higher-viscosity full synthetic oil, and the noise noticeably reduced. However, the key is still to disassemble and inspect the crankshaft to check for scoring on the journals or pitting on the bearings. Regular maintenance should include timely oil and filter changes, and avoid using low-quality lubricants.
Crankshaft abnormal noise should not be taken lightly. Common causes include: first, excessive wear of crankshaft bearings creating clearance; second, excessive axial movement of the crankshaft; third, connecting rod deformation or damage to big/small end bearings. It's recommended to immediately check engine oil level and pressure, as insufficient oil supply from the pump can cause severe wear. During repair, the engine needs to be disassembled to measure crankshaft roundness and concentricity - if the error exceeds 0.03mm, regrinding or replacement is required. Also check the condition of crankshaft oil seals, as oil leakage can also cause abnormal noises. If attempting DIY repair, prepare special puller tools, but beginners should seek professional mechanics for safer handling.
