What causes abnormal noise in a newly replaced motorcycle motor?
3 Answers
The abnormal noise in a newly replaced motorcycle motor can be attributed to the following reasons: Excessive clearance between piston and cylinder: The knocking sound from a newly purchased motorcycle engine is usually caused by excessive clearance between the piston and cylinder. During the power stroke of the engine, the piston is subjected to high-pressure gas forces, causing it to oscillate and knock against the cylinder wall, resulting in noise. Additionally, issues such as piston ovality, bent or twisted connecting rods, excessive tightness in the piston pin and connecting rod bushings (bearings), or big-end bearings can also lead to piston knocking. Problems with the ignition system: If this occurs, it is recommended to check the ignition system and fuel supply system. If the starter can operate normally, it indicates that the battery has power. Motorcycle engines are equipped with an ignition system, whose main components include the ignition coil and spark plug.
Last month I just replaced the motor on my motorcycle, but after starting it, there was a rattling noise. At first, I thought it was a quality issue with the motor, but later I found out that the mounting bolts weren't tightened properly, causing the motor to vibrate and hit the frame when running. Another time, the belt was too tight, pulling on the new motor's bearings and making a squeaking sound. Actually, when replacing a new motor, it's important to ensure precise alignment. If the gears aren't meshing properly or the bearings lack lubrication, it's easy to get noise. I recommend you turn off the engine and check the tightness of the bolts and the drive belt, and lubricate the chain while you're at it. If the noise persists, it's best to open up the motor and see if any internal parts are misaligned. If you can't handle this yourself, quickly take it to a mechanic.
I've repaired quite a few motorcycles with newly replaced motors that had abnormal noises, mostly due to installation issues. If the motor base screws are one turn short, it causes shaking and knocking. Over-tightened belts put extra pressure on bearings, and misaligned transmission gears make particularly noticeable clunking sounds. Additionally, new motors may have factory defects like unbalanced rotors or deformed bearing seals. When troubleshooting, first locate the sound by listening - metallic knocking means checking fasteners, high-frequency friction indicates transmission issues, while deep rumbling points to internal motor problems. Remember to power off before working, use a torque wrench for disassembly/reassembly according to manual specifications, and leave about a finger's width of slack in the belt.
