Starting at +41° 26' 40.00", -73° 5' 33.00" proceed north up the closed-off portion of road (unpaved and rutted/rocky): eventually coming through to pavement (Chestnut Tree Hill Rd). Bear right and 200 yards up, just passed the power line on the right is an access point for Seymour Reservoir No 4 (the northern most of the four). Turn in here and ride the earthen dam, traveling east, on the south end of #4. At the end, stay to the right and turn off where the old chain link gate is, cross the power line and continue down towards #3. Large hickory tree down across trail at end of this leg: lift over stay slightly to the right for #3.
When you reach #3, travel west along the south end and go left, up the hill (sort of) and left at a fork - then down a very steep and rocky trail, trying to stay on the high side(s). When this bottoms out, there is 150 yards of nice old growth Hemlock very pretty and very level... at the north end of #2, there is a confluence of trails and an involved beaver dam worth a visit: otherwise, travel south along the west side of #2 and turn at the south end to go east over the south end...
About 2/3 the way along this dam, there is a switchback right hand turn which goes down a single lane trail to Reservoir #1 (some nice industrial archeology out in the woods here - big culverts, pipes, shafts with petcock wheels every now and then). Ride long the eastern bank of #1 and make a left to cross the dam on the southern end, a left after you ride over the spillway then and begin the climb up to the lower access parking area (along Rt 42, just inside the Oxford town line). Not much of a steep grade but lo-o-o-ong... at the end there is a gate which requires a dismount and the gravel is pretty rutted, so I walk over to the pavement before mounting and riding back to the starting point along the unpaved road.
Here's a map link (it goes to live.com which has some amazing bird's eye level photographs of the entire area, along with two levels of bird's eye zoom!)