If you have already replaced the battery, stator, and regulator rectifier on your motorbike and it still isn't charging, there could be a few other possible reasons for the issue:
Faulty wiring or connections: Check all the wiring connections between the battery, stator, regulator rectifier, and the charging system. Ensure they are properly connected, secure, and free from corrosion. Faulty or loose connections can prevent proper charging.
Faulty alternator rotor: The alternator rotor is responsible for generating the electrical current in the stator. If the rotor is faulty or damaged, it may not produce enough electricity to charge the battery. Inspect the alternator rotor for any signs of damage or wear, such as broken wires or excessive heat.
Faulty ignition switch: The ignition switch controls the electrical system on your motorbike. If the ignition switch is faulty, it may not allow the charging system to function properly. Check the ignition switch for any signs of damage or malfunction, and consider testing it or replacing it if necessary.
Voltage regulator compatibility: Ensure that the voltage regulator you installed is compatible with your specific motorbike model. Different bikes may have different voltage requirements, and using an incompatible regulator could result in improper charging.
Grounding issues: A poor or faulty ground connection can disrupt the charging system. Check the grounding connections between the battery, frame, and other components. Make sure they are clean, tight, and secure.
Other electrical components: Faulty or malfunctioning electrical components such as a faulty starter relay or a short circuit in the wiring system can also affect the charging system. Inspect other electrical components related to the charging system and test or replace them if necessary.
If you have checked all of these potential issues and are still unable to identify the cause of the charging problem, it may be beneficial to consult a professional mechanic or an authorized service center for further diagnosis and assistance.