You're passing through Ithaca, NY and make sure to stop there for a meal. That city has a very diverse selection of good eats in the Ithaca commons and collegetown area near Cornell University. You can also take a side trip off the bike and walk through some of the gorges.
When in NH, go south on 16 from Gorham and climb Mt Washington. The road going up is pretty nice and the view is supposed to be great on a clear day. I went up there last year on the 919.
Along your way back into NY, you'll be crossing over the Bear Mountain Bridge onto the west side of the Hudson river. Instead of going north on 9W, go south and then hang a right onto Seven Lakes Drive. This will take you up the side of Bear Mountain along a great twisty stretch and then you can go up on Perkins Memorial Drive to the top of Bear Mountain. It's a popular day trip for NYC riders as this these are the closest "twisties" excluding highway offramps within 50 miles of the city.
After Bear Mountain, continue on Seven Lakes Drive west where it will then dip south into Harriman State Park. Head south along the lakes and then go West on Rt 106 for more twisties. Rt 106 will reconnect with 17A and you can continue your route as planned. Emerald Point restaurant next to Greenwood lake just off your route on 17a is a popular lunch spot for motorcyclists.
If you plan on going into NYC, I could show you around a bit. Also, if you're going to be around Bear Mountain on a weekend, I might be able to come up and take you on more of those roads.
Hope you enjoy your trip!
2012 Yamaha Super Tenere
2001 Honda Blackbird
2007 Honda 919
49/50 visited on two wheels. 1 more to go!