Two hours between flights while having to change terminals at JFK is very risky. If everything is on time, there's no lines at security, and you can run between flights you'll probably be ok, but it could just as easily go the other way. And, one thing to keep in mind if you are on separate tickets and have to recheck a bag, many airlines have 45-60 minute bag check cut offs. I've had short connections a JFK that I would have made but for missing the bag check cut off.

Hope your flights are on time...