A motorized bicycle is a bicycle with an attached motor and transmission used either to power the vehicle unassisted, or to assist with pedaling. The earliest attempts at building motorized bicycles began in the 1860s with steam engines attached. It did not succeed, however, until the invention of the internal combustion engine (ICE) powered by gasoline.

Thomas of Buffalo in NY began selling gasoline engine kits in 1896. He later formed the Thomas Motor Company and sold motor-assisted bicycles under the Auto-Bi name. Auto-Bi is considered the first motorized bike produced in the U.S. The riding position centered over the pedals was changed by moving the feet forward to rest on pegs or platforms to improve comfort and control.
Suspension in the front, as well as the back on some, offered better control at higher speeds. Motorized bicycles began to be produced without pedals by 1915 introducing the first motorcycle. Vincenti Piatti, Italian, designed a 50 cc engine for driving portable lathes which offered the Mini Motore used to power a bicycle and was later produced by Trojan.
Motorized bicycles today are developed as complete designs and add-on motor kits by hobbyists and manufacturers. Mopeds arrived in the U.S., the U.K., and other countries in the 1960s after they became popular in France and Italy. New machines were marketed by Honda, Yamaha and other companies that were operable without a license.
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Legal definitions using ICEs varies from nation to nation, and some rules and regulations are local. Motor-driven cycles are off-road vehicles in the U.S., and under federal law, are not considered motorcycles. Whether or not motor driven cycles are legal on public roads is determined by the laws of the state. Regulations are determined by the laws of each state and local jurisdiction.
Motorbikes do not have to be registered and licensed nor taxes paid in several states to ride them on the roads. There are, however, certain restrictions to follow. Multi-use recreational paths and high speeds may be off limits, safety equipment may be required such as a helmet, and there could be limitations on the roadways.
Motor-driven bicycles gained in popularity during the late 1990s due to inexpensive 2-stroke engines and chain-drive transmissions from China. Emissions laws in the U.S. have made it increasingly difficult for traditional 2-stroke engines to pass requirements. Tanaka Inc. has introduced a clean-burning Pure Fire line of 2-stroke motors. The development of the 4-stroke gasoline engine is on the rise because it uses less fuel and oil, creates less emissions and tends to be quieter.
Safe Riding!