Carmichael and Windham will be the only former Unadilla winners in the 250 class, with Ricky shooting for his fourth win at the historic circuit.
Meanwhile, in the 125cc ranks Kawasaki's James Stewart will attempt to become the first three-time Unadilla 125 winner.
However, the series leader is coming off his first motocross loss this year when a first turn pile-up, a further fall and subsequent clutch damage in the second moto at Red Bud on July 4, caused Stewart to retire from the race and cost him his chance at a perfect season.
Boost Mobile Yamaha's Mike Brown was in the right place at the right time in Michigan, and was able to take advantage of Stewart's unlucky break for his first victory in over a year. Brown, who is 31 points behind Stewart in the 125 standings, is looking to earn his first victory at Unadilla.
New York fans will have a number of home state riders to root for with veteran Bruce Stratton, of Clifton Springs, racing a limited schedule in the series, but having already scored a solid 15th-place finish in Southwick a month ago. Stratton feels at home at Unadilla and will be aiming for a top-10 finish.
In the 125 ranks New York riders Ryan Mills, Paul Carpenter and Brian Gray are all threats to score podium finishes. Mills has already scored a top-10 result this year on his Amsoil/Chaparral Honda, is ranked 12th nationally and hoping to improve on his standing with a good result this weekend.