Yes, it is normal for a motorcycle battery voltage to drop when cranking the engine. When you start the motorcycle, the starter motor draws a significant amount of electrical power from the battery to turn the engine over. This high current draw causes a temporary drop in battery voltage.
The battery voltage drop during cranking is a result of the battery's internal resistance and the power demands of the starter motor. The internal resistance of the battery causes a voltage drop when there is a heavy load applied to it. As a result, the battery voltage can drop considerably, often below 12 volts, during the cranking process.
Once the engine starts and the alternator or generator begins to produce electrical power, the battery is recharged, and its voltage returns to a normal level. The charging system of the motorcycle then maintains the battery's charge and provides power to the electrical components while the engine is running.
It's worth noting that while a slight voltage drop during cranking is normal, a significant drop or a battery voltage that remains low after starting the engine could indicate an issue with the battery or charging system. If you notice persistent starting problems or have concerns about your motorcycle's electrical system, it is advisable to have it inspected by a qualified mechanic.