Yes, it is normal for the voltage of a 12V motorcycle to increase when the engine is running at higher speeds compared to when it is at idle. The voltage regulation system in motorcycles is designed to ensure that the electrical system receives a stable and appropriate voltage level for charging the battery and powering the motorcycle's electrical components.
At idle, the engine's RPM (revolutions per minute) is typically lower, which means the alternator or generator, responsible for charging the battery and providing electrical power, may not be operating at its maximum output. As a result, the voltage may be slightly lower, often around 13-14V, to meet the electrical demands of the motorcycle's systems while still charging the battery.
This higher rotation speed allows it to produce more electrical power, leading to an increase in the output voltage. It is not uncommon for the voltage to rise to around 13-16V or even slightly higher during higher engine speeds.
The higher voltage is necessary to compensate for the increased electrical load caused by the motorcycle's systems, including the lights, ignition, fuel injection system, and other accessories. Additionally, the higher voltage ensures that the battery continues to receive a charge, maintaining its state of charge while providing enough power for the electrical components.
If you suspect there is an issue with the voltage regulation system or notice excessively high or low voltage levels, it is advisable to consult the motorcycle's owner's manual or seek professional assistance from a qualified mechanic to diagnose and address any potential problems.