The Honda TT Legends team will miss the Ulster Grand Prix at Dundrod in August due to a date clash with the Endurance World Championship.
Official Honda stars John McGuinness and Simon Andrews, plus Gary Johnson and Cameron Donald will compete in the Endurance World Championship in 2012 in addition to the North West 200 and Isle of Man TT this year.
However, the series clashes with the Ulster Grand Prix on August 11 at Oschersleben in Germany, effectively ruling out the appearance of all four Honda riders.
The quartet will represent the Honda TT Legends team in the championship, with McGuinness and Andrews riding the team's official machines on the roads.
Donald will race the Wilson Craig Hondas at the NW200 and TT with Johnson Honda-mounted possibly on Clive Padgett's machines or entered under the East Coast Racing banner.
Both McGuinness and Keith Amor rode for the Legends team at the Ulster GP in 2011 after missing the North West 200 due to a clash with an Endurance round at Albacete.
Scotsman Amor retired from road racing last month due to an ongoing shoulder injury which he sustained at the Isle of Man TT last year.
Ulster Grand Prix chief Noel Johnston is promising fans a stellar line-up at the event, despite the unfortunate date clash.
"It's unfortunate, but we confirmed our date early this
year and the Endurance World Championship dates were only completed recently.
"A round clashes with the Ulster Grand Prix, so that means we will lose John McGuinness and Simon Andrews, but we haven't given up hope that one of either Gary Johnson or Cameron Donald will be able to make the event.
"But we will still have a first-class line-up this year, of that you can be certain."
The Ulster GP celebrates its 90th anniversary this year.