When buying a used 50cc motorcycle, it is important to look for any mechanical or structural issues that could become safety hazards, such as bad brakes or missing engine parts. It is also important to make sure that the bike is the right size for the intended rider.
50cc motorcycles are small in size and ideal for children just beginning to learn how to ride. If the motorcycle is intended for a beginner, it is very important to verify its safety before allowing anyone to ride it. A beginner is unlikely to know how to react if the bike experiences issues during operation and can easily get hurt. The used motorcycle should be inspected by a licensed mechanic to ensure that all parts are in proper working order and that there are no hidden issues with the frame or other components. Once it has passed inspection, an experienced rider should also test drive the bike to look for other issues that may not be apparent.
Making sure the motorcycle isn't too small for the rider is also important, because riding a bike that is not the appropriate size can cause discomfort in the rider. If the bike is too small, a larger size may be necessary, but a bike that is too large for the rider to control easily is dangerous.