Ulsterman William Dunlop headed a Tyco Suzuki one-two with Guy Martin as the pair dominated the opening Supersport 600 race at the Armoy road races.
The pair battled for the lead throughout, dropping Scottish star Keith Amor at the half-way point of the six-lap race with Dunlop eventually taking the victory by 0.8s over his team-mate.
Isle of Man TT star Michael Dunlop was fourth on his MD Racing Honda, eight seconds down on the Suzuki pair, with Manx rider Dan Kneen and James Cowton completing the top six.
Dunlop, who missed the Southern 100 meeting as he recovered from a broken leg sustained in a spill at the Isle of Man TT, said: “I really enjoyed that race with Guy. It was fair and honest and the wee 600s were really flying. A one-two shows the strength of the GSX-R600.
“Let's hope we can do something similar tomorrow in both the 600 and Superbike classes.”
Lincolnshire favourite Martin, who clinched the Solo Championship title for the second year in success at the Southern 100 earlier this month, added: “Second is first loser as they say, but yes a good race with William and fair play to him. There wasn't much in it at the end but tomorrow is another day and we'll give it a good go around this mint little circuit.”
Michael Dunlop headed the times in the Superbike class on his Superstock BMW, with his brother William and Martin second and third respectively.
A second Supersport 600 race plus both feature Superbike events will be held as part of the main race schedule at the Armoy meeting in Northern Ireland on Saturday.