If your motorcycle stalls or experiences coughing when you turn on the headlight and/or turn indicator, particularly at lower RPMs, it may indicate an electrical or charging system issue. Here are a few possible explanations for this problem:
Insufficient electrical power: When you turn on additional electrical components such as the headlight and turn indicators, it increases the electrical load on the motorcycle's system. If the charging system is not providing enough power to meet this increased demand, it can result in a drop in voltage, affecting the ignition system and causing the engine to stall or run poorly at lower RPMs.
Weak battery: If your motorcycle's battery is weak or not holding a charge properly, it may struggle to provide enough power to both the electrical components and the ignition system simultaneously. This can lead to a loss of power and stalling when the lights are turned on.
Loose or corroded electrical connections: Poor electrical connections can lead to voltage drops and intermittent power supply. Check the battery terminals, wiring connections, and ground connections to ensure they are clean, tight, and free from corrosion.
Faulty regulator/rectifier: The regulator/rectifier is responsible for converting the alternator's output to charge the battery and regulate the electrical system's voltage. If the regulator/rectifier is malfunctioning, it may not be providing sufficient power to the electrical system, leading to issues like stalling when additional loads are applied.
It's advisable to have a qualified mechanic inspect your motorcycle to diagnose the specific cause of the problem. They can perform tests on the charging system, battery, and electrical components to identify any faults and recommend the necessary repairs or replacements.