Oklahoma Statutes Citationized
**Title 47. Motor Vehicles
****Chapter 1- Definitions of Words and Phrases
********Section*1-104 - Bicycle, Electric-Assisted Bicycle, and Motorized Bicycle
Cite as: O.S. §, __ __
A. A bicycle is a device upon which any person or persons may ride, propelled solely by human power through a belt, chain, or gears, and having two or more wheels, excluding mopeds.
B. An electric-assisted bicycle is any bicycle with:
1. Two or three wheels; and
2. Fully operative pedals for human propulsion and equipped with an electric motor:
a. with a power output not to exceed one thousand (1,000) watts,
b. incapable of propelling the device at a speed of more than thirty (30) miles per hour on level ground, and
c. incapable of further increasing the speed of the device when human power alone is used to propel the device at a speed of thirty (30) miles per hour or more.
An electric-assisted bicycle shall meet the requirements of the Federal Motor Vehicle Safety Standards as set forth in federal regulations and shall operate in such a manner that the electric motor disengages or ceases to function when the brakes are applied.
C. A motorized bicycle is any bicycle having:
1. Fully operative pedals for propulsion by human power;
2. A power drive system that functions directly or automatically without clutching or shifting by the operator after the drive system is engaged; and
3. A combustion engine with a piston or rotor displacement of eighty (80 cu cm) cubic centimeters or less, regardless of the number of chambers in the engine, which is capable of propelling the bicycle at a maximum design speed of not more than thirty-five (35) miles per hour on level ground.
D. As used in this title, the term "bicycle" shall include tricycles, quadcycles, or similar human-powered devices, electric-assisted bicycles, and motorized bicycles unless otherwise specifically indicated.
There is your Oklahoma law. You do have an 80 cc limit. You can't manually clutch or manually shift engine gears. A shift kit would make your bicycle gears engine driven gears. However the law doesn't say the engine driven gears can't be shifted automatically. Its a legal loophole.