Motorized bicycles cannot be registered in New York according to state law.
A motorized bicycle is classed as a Motor-assisted Bicycle - a bicycle to which a small motor is attached. A motor-assisted bicycle doesn’t qualify for a registration as a motorcycle, moped or ATV and doesn’t have the same equipment.
You cannot register or operate Motor-assisted Bicycles in New York on any street, highway, parking lot, sidewalk or other area in New York State that allows public motor vehicle traffic. You may be arrested if you do.
Some members have had success registering their motorized bicycles as a Class C moped with a top speed of 20mph or under. You do not need an inspection to register your a Class C moped. You will need a chassis number though. Read the discussion thread to find out more.