Revving a motorcycle in neutral, when done occasionally and within reasonable limits, is generally not harmful to the engine. However, excessively high revving or prolonged revving without load can potentially cause some issues. Here are a few points to consider:
Engine Lubrication: When the motorcycle is in neutral, the engine is not under load, which means there is less oil pressure being generated. This can affect the lubrication of engine components, particularly the bearings. Prolonged or excessively high revving can reduce oil circulation and potentially cause inadequate lubrication, leading to increased wear over time.
Overheating: Revving the engine in neutral for an extended period can lead to increased heat buildup. The cooling system may not be able to dissipate the heat efficiently without airflow generated by riding. Overheating can potentially damage engine components, such as gaskets, seals, and even cause the engine to seize if pushed to extreme temperatures.
Clutch Wear: Revving the engine in neutral at very high RPMs and repeatedly "blipping" the throttle can put additional stress on the clutch. While the clutch is disengaged in neutral, the clutch plates are still spinning at higher speeds. Excessive revving can cause increased wear on the clutch components, potentially reducing its lifespan.
Noise and Environmental Considerations: Revving the engine excessively in neutral can create unnecessary noise, which may disturb others around you. It's important to be mindful of noise regulations and respect noise-sensitive areas. Additionally, excessive revving can contribute to increased exhaust emissions, which is not environmentally friendly.
In summary, occasional and moderate revving in neutral is unlikely to cause significant harm to the motorcycle's engine. However, it's advisable to avoid prolonged or excessively high revving without load to minimize potential risks and unnecessary wear on engine components. Regular riding conditions provide better airflow, engine cooling, and load on the drivetrain, which is more ideal for engine operation.