For the second race in a row, poleman Tom Sykes got stuck on the factory BMW, involving the three protagonists of the championship.
Of the trio, Yamaha’s Razgatlioglu led the field in Turn 1, closely followed by Scott Redding and Rea, second and third respectively.
Rea quickly sent Redding’s Ducati for second place, then proceeded to chase after Razgatlioglu, diving inside the Yamaha rider on Turn 1 at the start of Lap 2.
But the six-time champion ran a bit wide in the turn, allowing Razgatlioglu to run alongside him in Turn 2 before regaining the lead in the next right-hand turn.
The battle between the two was interrupted when the race was signaled with a red flag for a major accident involving Mahias and Davies at Turn 11, with the Go Eleven runner scheduled to be taken to the medical center on a stretcher for mandatory checkups.
A five-lap sprint race followed, with the starting grid based on the order in which they were racing at the end of the last completed lap.
Rea was on the move on the restart, his Kawasaki brushing past Razgatlioglu’s Yamaha as they both made quick breakaways. There was more contact coming off Turn 1, with Rea hitting Michael Ruben Rinaldi’s second Ducati and forcing him off the track.
Razgatlioglu then ran wide into Turn 3, allowing Rea to pass and take the lead. Razgatlioglu fired back and the two riders raced side by side in Turns 6 and 7, but the Kawasaki ace somehow retained the lead as rival Yamaha briefly slipped behind the Honda in charge of Alvaro. Bautista.
Behind the top three, Andrea Locatelli hooked up Alex Lowes’ other Kawasaki in the long left-hand corner of Turn 10, falling off his bike and also knocking out his Yamaha teammate Kohta Nozane.
Ducati’s Redding also had the misfortune of running right behind the trio and had to take evasive action, falling to the back of the field.
Back at the forefront, Rea took advantage of the chaos that ensued behind him to build himself a comfortable 0.5 second buffer.
Razgatlioglu managed to get Bautista back for second place and close the gap to the race leader with the fastest lap of the penultimate lap, but was not close enough to make a move in the last ride on Ulsterman.
Rea eventually retained the win by 0.2 seconds and clinched pole position for the final race of the weekend, while Bautista finished third behind Razgatlioglu to secure Honda’s first podium of the season.
Lowes placed fifth ahead of Rinaldi and Saturday star Axel Bassani on the Motocorsa Ducati, with Leon Haslam (Honda), Garrett Gerloff on the sole survivor of GRT Yamaha, Christophe Ponsson (Gil Yamaha) and Leandro Mercado (MIE Honda) completing the top 10.
Redding finished in 15th place after being caught in the collision between Locatelli and Nozane, dealing another blow to his already distant title hopes.
Neither BMW finished the race after Michael van der Mark knocked out teammate Sykes in the first lap.