Unusual noises from the motor can have many causes. Is your motor being subjected to severe stress from riding uphill, a heavy load or heat?This may cause your motor to overheat and emit noises that are louder than normal.
You can protect your motor by using one foot to support heavier loads like on a conventional scooter.This also applies to starting off. When starting off on your scooter from a standing position, the motor has to apply significantly more force to get you and the scooter going than when using one foot to pick up a bit of speed before using the throttle. This also reduces power consumption, giving you a longer range!