Michael Dunlop rode through the pain barrier to secure a brace of wins at the Cookstown 100 road races, where Derek Sheils was also a double winner.
Dunlop, who will undergo surgery this week on an arm injury sustained at Brands Hatch last week, won Supersport 600cc race two and the Supertwins.
Sheils took the flag in the opening Supersport outing and the Open race.
Debutant, Manxman Dan Kneen, won the feature race from the second group by 0.3 seconds from William Dunlop.
Kneen, riding for John Burrows's BE Cookstown Racing team, took the victory on corrected time from the Tyco TAS Suzuki rider, who crossed the line first, with Mullingar's Derek McGee third.
The Manx rider said it had been a "dream debut" at Cookstown.
He said: "I knew I had it in me and it was time to prove it to everyone else".
Michael is struggling with a suspected broken arm sustained in qualifying for last week's British Superbike championship round.
He is likely to miss next week's second round at Oulton Park and faces a race against time to be fit for the North West 200.
"I am riding through the pain barrier - and probably shouldn't be here at all, but I didn't want to miss the first road race of the season. I really surprised myself as I didn't think I would be competitive. I didn't feel the injury during the Supersport race. But I feel the pain now.
"I may need to have my arm plated during surgery next week. I hope it goes smoothly and am confident of being ready for the North West - I simply have to be fit."
Dubliner Sheils laid down an early marker at the Orritor circuit by winning Friday evening's Supersport joust, with runner-up McGee 0.2 seconds behind, followed by William Dunlop and brother Michael.
The CD Racing Kawasaki pilot made it two wins from two starts by taking the flag in the Open race, 0.7 seconds ahead of McGee and William. Michael retired on his BMW Superstock machine on lap six.
The second Supersport race saw the younger of the Dunlop brothers produce a heroic performance to come through from ninth on lap three and then pass second-placed man McGee and third-place finisher Sheils on the final circuit.
William Cowden won the Moto3/125cc race and John Ella came home ahead of Michael Sweeney and Tommy Henry in the 250cc class.
James Cowton and Jamie Hamilton made up the podium positions in the Supertwins.