Derek Sheils secured his fifth successive victory on the Burrows Engineering Racing Suzuki at the KDM Hire Cookstown 100 on Saturday.
Sheils won the Open A race on corrected time by almost five seconds after starting from the B Group.
The Dublin rider had qualified in 12th place for the race after suffering an engine blow-up on the first lap of qualifying on Friday.
Sheils claimed the win from Michael Dunlop, who was the first rider over the line on the Tyco BMW.
The Ballymoney man was making his road racing debut on the S1000RR after agreeing a deal with the Moneymore-based team to compete in the Superbike class this season.
Skerries rider Michael Sweeney was third on the MJR BMW ahead of pole man Derek McGee, who was riding the 600cc B&W Kawasaki.
Adam McLean and James Cowton were fifth and sixth respectively for the McAdoo Racing team.
The race was delayed for over an hour to allow the course to dry following rain showers.
Earlier, Michael Dunlop won his first race of the new season as he powered the MD Racing Honda to victory in the non-championship Invitational Supersport event.
The race was carried over from Friday evening, when it was halted due to low sun.
Dunlop came through to take the lead from McLean, winning by 2.8 seconds.
Yorkshire rider Cowton competed the rostrum followed by Sheils, Sweeney and Paul Jordan.
William Dunlop was a retirement in the Open and Supersport races on his Temple Golf Club Yamaha machines.
The Irish Championship Supersport race was won by Cowton, who headed up a McAdoo Racing one-two from team-mate Adam McLean at the team’s home meeting.
Sheils (Yamaha R6) finished in third ahead of Michael Dunlop, Derek McGee and William Dunlop.
The race was cut short due to a red-flag incident. The rider involved was not seriously hurt.
Mullingar man McGee was a comfortable winner of the Moto3/125GP race on the Joey’s Bar Honda from McLean by over seven seconds, with Paul Robinson in third.