Each state has various laws below is a summation of my state
Texas
The DMV may refuse to register a motorcycle and may suspend or revoke the registration if the DMV determines that the motorcycle’s braking system does not comply with safety requirements.
An operator of a motorcycle must ride on the permanent and regular seat attached to the motorcycle.
A passenger may ride only on the permanent and regular seat, if designed for 2 persons, or on another seat firmly attached to the motorcycle behind or to the side of the operator. No passengers under age 5 permitted.
A motorcycle, including a motor-driven cycle,
must be equipped with not more than 2 headlamps, at least 1 tail lamp, a separate rear license plate lamp, at least 1 stop lamp, and at least 1 rear red reflector.
A motorcycle, other than a motor-driven cycle, must be equipped with multiple-beam headlamps.
A motorcycle may not be operated at any time unless at least 1 headlamp is illuminated.
The operator and any passenger on a motorcycle or moped are required to wear an approved helmet. However, a person is exempt from wearing a helmet if the person is at least 21 years old, and has successfully completed a motorcycle operator and training safety course or is covered by at least $10,000 in medical benefits for injuries incurred as a result of an accident while operating or riding on a motorcycle.
2019 an additional note of no LED type lights pointing down on the bike