Rising roads start Dean Harrison from Bradford, regarded as one of the sport's hottest properties, has been strongly linked with a move to Northern Ireland's Mar-Train Racing team, which will lead Yamaha UK's official roads challenge in 2015 and 2016.
Harrison rode Mar-Train Racing's Supersport machine this year at the international races plus the Southern 100 and Scarborough meetings.
A statement issued by RC Express Racing on Wednesday evening said: "Isle of Man TT race winners RC Express Racing have today (Wednesday) announced that they have parted company with Dean Harrison for 2015 with the Bradford rider opting to pursue other options and challenges for the season ahead.
"The duo had a verbal agreement in place for 2015 but the father and son team of Roy and Ben Constable have decided not to stand in Harrison's way and reluctantly, though amicably, agreed to release him.
"The Bristol-based team joined forces with the now 25-year-old mid-way through the 2012 season after his impressive performances at that year's TT and the partnership went on to experience a meteoric rise to the very top of the road racing ladder, improving their results with each and every outing as well as repeatedly setting personal best laps.
"Together, they enjoyed an extremely successful two and a half years, the undoubted highlights being a start to finish victory in this year's Lightweight TT race as well as a close second place to Michael Dunlop in the Superstock race on their immaculately-prepared Kawasaki machinery.
"In total, the partnership claimed an impressive five top eight finishes in two years of racing at the TT, only suffering one DNF from their seven races together. Harrison also became one of only 14 riders to lap the 37.73-mile mile course at more than 130mph when he lapped at 130.261mph from a standing start in this year's Senior race.
"Elsewhere, a rostrum was taken at the 2014 Ulster Grand Prix, where Harrison became the fastest newcomer in 2012 becoming the first to break the 130mph barrier in the process, whilst numerous race wins and lap records were taken at the Southern 100 where Dean won five of the seven races he started in 2014," the statement added.
"Meanwhile, there was also notable success achieved at Oliver's Mount, Scarborough with Harrison winning the Cock o' the North Trophy in both 2013 and 2014.
"Everyone at RC Express Racing would like to thank Dean for his effort and commitment during his time with the team and wish him all the very best for the future.
"An announcement will be made in due course on RC Express Racing's schedule and plans for 2015."