A bicycle with a gas engine attached is illegal in NY:
http://www.nydmv.state.ny.us/DMVfaqs.htm#MOPEDS
Motorized Scooters, Mini-Bikes, Dirt Bikes, Go-Karts, Motor Assisted Bicycles
You
cannot register any of the motorized devices from the list below in NYS. You
cannot operate these devices on sidewalks, public streets or highways in NYS. These devices are motor vehicles, but they do not have the correct equipment or design for operation on roadways.
- Motorized Scooter - a device with a motor attached and a handlebar for a standing rider. An example of a motorized scooter is the device called the Go-pedŽ.
- Mini-bike - a small, motorized device with two wheels and created for off-road use. A mini-bike does not qualify as a moped, a motorcycle or an ATV.
- Dirt Bike - a motorized device like a motorcycle, but created for and used for off-road use. Some "dirt bikes" qualify as an ATV. These vehicles can register and operate off-road as an ATV.
- Go-Kart - a small, motorized device with four wheels, created for off-road use. You cannot register a go-kart as a motor vehicle or ATV because a go-kart does not have the same equipment.
- Motor-assisted Bicycle - a bicycle to which a small motor is attached. A motor-assisted bicycle does not qualify for a registration as a motorcycle, moped or ATV and does not have the same equipment.
These devices are not allowed on any street, highway, parking lot, sidewalk or other area that allows public motor vehicle traffic. You are subject to arrest if you operate one of these motorized vehicles and do not have a registration, driver license, inspection, insurance or correct equipment. The DMV can not provide any information about operation of these devices on private property. Contact the local authorities and property owners.
And you can't post on bike forums any more
A.