If your motorcycle's back wheel is spinning while it's on a stand and in neutral, it typically indicates an issue with the clutch or the transmission. Here are a few possible causes:
Clutch adjustment: Improper clutch adjustment can lead to the clutch plates not fully disengaging when the lever is released. This means that even when the clutch lever is pulled in, some power is still being transmitted to the rear wheel, causing it to spin. Adjusting the clutch cable or hydraulic system to ensure proper disengagement can help resolve this issue.
Clutch plates or springs: Worn or damaged clutch plates or springs can prevent the clutch from fully disengaging, resulting in power transmission to the rear wheel even when the bike is in neutral. Over time, clutch plates can become worn, warped, or glazed, reducing their ability to separate properly. Replacing the clutch plates or springs can rectify the problem.
Clutch cable or hydraulic system issues: If there are issues with the clutch cable or hydraulic system, such as stretching, fraying, or air in the hydraulic line, the clutch may not fully disengage. This can cause the rear wheel to spin. Inspecting and repairing or replacing these components can help address the issue.
Transmission problems: Internal issues within the transmission, such as worn gears or shift forks, can cause the transmission to not fully engage neutral, even when the shifter is in the neutral position. This can result in power being transferred to the rear wheel. If this is the case, it may require a more in-depth inspection and repair by a professional mechanic.
It's important to note that riding a motorcycle with a spinning rear wheel while it's on a stand can be dangerous. If you're unable to diagnose or fix the issue yourself, it's recommended to consult a qualified motorcycle mechanic who can properly inspect and repair your motorcycle.