What is the decibel level of motorcycle noise?

[McBrooklyn]

The noise limit for two-wheeled motorcycles with a displacement greater than 50ml and less than or equal to 80ml is 75dB during acceleration, while for those with a displacement greater than 80ml and less than or equal to 175ml, the limit is 77dB. The reasons for motorcycle noise are as follows: During cold starts: Due to the larger gap between the cold-contracted piston and the cylinder wall, slight knocking sounds may occur. These sounds diminish and disappear as the temperature rises. Poor lubrication conditions: When starting the engine, poor lubrication conditions and low oil pressure result in insufficient oil film formation on the cylinder walls, causing direct contact between the piston and the cylinder body. After a 3-5 minute warm-up period, normal lubrication is restored, and the noise decreases or disappears.