Take my advice, it's a h3ll of a lot easier, just to
buy a moped (if you live in NY), then to try to get away with registering a bike with a gas motor on it...
Save yourself a lot of worries, headaches and possible jailtime, until the law is changed.
It would be awesome to get away with the inherent inexpensiveness of a bike with a gas motor (approx. $200) then having to deal with the expense of a moped (approx $800 and up) and registration, titling, insurance, etc, etc, etc, but that just ain't the case in NY.