When you hear a whining sound from the starter motor without it engaging when you press the start button on your BMW K75 motorcycle, it typically indicates an issue with the starter system. Here are a few possible reasons for this problem:
Faulty starter solenoid: The starter solenoid is responsible for engaging the starter motor with the engine's flywheel. If the solenoid is malfunctioning or worn out, it may not engage properly, resulting in the whining noise. A defective solenoid may need to be replaced.
Weak battery: Insufficient power from the battery can prevent the starter motor from engaging properly. Check the battery's voltage using a multimeter. If it is below the recommended level, recharge or replace the battery as necessary.
Loose or corroded electrical connections: Loose or corroded connections in the starter circuit can cause a lack of power delivery to the starter motor. Inspect the connections between the battery, starter solenoid, and starter motor, ensuring they are clean and secure.
Faulty starter motor: The starter motor itself may be damaged or worn out, preventing it from engaging with the engine. In such cases, the starter motor might need to be replaced.
Clutch or neutral safety switch issue: Some motorcycles have safety switches that prevent the starter motor from engaging if the clutch lever is not pulled in or the bike is not in neutral. Ensure that the clutch lever is fully pulled in or try starting the bike in neutral.
If you are unsure about diagnosing or repairing the issue yourself, it's recommended to consult a qualified motorcycle mechanic or BMW service center. They will have the expertise and necessary tools to identify and resolve the specific problem with your BMW K75 motorcycle's starter system.