In western MA Rt.116 from Amherst to Adams is good, especially the middle section. Rt.2 from the MA/NY state line is really good. The road climbs through a nice mountain pass. The NY side was a little bumpy the last time I was there, but if they've repaved it in the last year or so it would be awesome. Some parts of Rt.2 between the state line and Greenfield, MA are excellent, though there is a fairly heavy volume of traffic if you hit it at the wrong time (Rt.116 is only lightly travelled on the other hand.) Pelham Rd. which runs between Amherst and Pelham is nice. It ends at Rt.202 which runs up the west side of the Quabbin Resevoir; a good ride also.
In southern Vermont, Rt.100 is a good bet (as is Rt.9 between Rt.100 and I-91). Route 100 is pretty good all through the state although it gets a little tame through the middle part (but has good New England scenery). The best parts for twisties are the part just north of Rt.9 and the part between Stockbridge and Waitsfield . *Not to be missed* is what I and my buddies call the "figure eight" ride of Vermont. Rt.100 makes up the eastern side of the figure eight. As you head north there are three east-west roads which cut across the Green Mountain National Forest and intersect with 100. Each of these roads is excellent and all were freshly paved in 1994 (drool, drool!). The southern-most crosscut is Rt.73 which goes to Brandon. It is possible to bypass the town, but the name of the side road escapes me. The next one you come to as you head north is Rt.125. A dandy! It cuts across from East Middlebury to Hancock. The last one (and possibly the best) is Rt.17. This one goes through Appalachian Gap as it cuts from Waitsfield to Bristol. If you couple the three "cut across" roads with Rt.100 on the east and Rts.116 and 7 on the west side, you get a crude figure eight. This is the best riding I have found in all of New England.
You may also want to check out Rt.110 between East Barre and Royalton - it parallels Rt.100 to the east of the figure eight area. It, too, was freshly paved last summer. Another good ride is Rt.108 from Stowe through Smugglers' Notch.
A good 250 (+/-) mile loop consists of the following: Start in Lincoln, NH and take the "Kanc" (Kancamagus Highway, Rt.112) East. This is pretty good as a lot of the western slope was repaved in '93 or '94. Tourist traffic can be tiresome if you hit it at the wrong time. The road ends in Conway. Take Rt.113 North; you'll cross over into Maine, but keep going! This road eventually goes through Evans Notch. This is an excellent stretch of road; it gets all narrowed down and shoots you through a canopy of birch trees up one side and down the other. Road ends at Rt.2. Take Rt.2 West to Gorham, NH and then onto Rt.16 North. Rt.16 parallels the Androscoggin River and gets really good once you get past Berlin. It, too, had some 10 miles or so of fresh pavement in '93 or '94. Take this one all the way to Errol. In Errol turn West onto Rt.26. Take this to Colebrook, NH. You'll pass through Dixville Notch on your way - yet another great reason to ride a motorcycle! From Colebrook cross over the Connecticut River into Vermont and join Rt.102 South. Rt.102 on the Vermont side of the river is much better (and less traffic) than Rt.3 on the NH side. Follow Rt.102 down to Rt.2 and then cross back over the river into Lancaster, NH. Get on Rt.3 South and follow this down to Lincoln, NH (your starting place). On the way you'll go through Franconia Notch which affords much delightful scenery. It doesn't get any better in the state of New Hampshire.