Michael Dunlop was quickest in Tuesday's sun-kissed opening practice session at the North West 200.
The Ballymoney man clocked 121.65mph in the Superbikes to pip Alastair Seeley.
Carrickfergus rider Seeley topped the Supersport times, with Michael Rutter fastest in the Superstocks and Martin Jessop heading the Supertwins class.
Lincolnshire's Ben Wilson suffered a broken leg after coming off his Aprilia machine at Mill Road roundabout in the final minutes of Superstock practice.
The 34-year-old, in his second year at the North West, was scheduled to make his Isle of Man TT debut next month.
Seeley is level on 15 victories with Robert Dunlop ahead of racing on Thursday night and Saturday.
Michael Dunlop, who was happy with his practice outing on a Buildbase BMW Superbike, aims to prevent Seeley from moving clear of his father's tally.
"I'm glad the bike's in good shape and hopefully we can get some good results this week," said the four-times winner on the Triangle circuit.
"After a difficult 2015 we have a decent bike now and the team is getting stronger and stronger.
"And yes, I'll be out to stop Alastair breaking the record if possible."
Seeley was fastest on 121.38 until a late burst from Dunlop, while Ian Hutchinson (120.89) completed the top-three.
Seeley dominated the Supersport session and his 116.41 was well clear of Hutchinson (114.80) and Jessop (114.41) in third.
Rutter's 121.847 is an unofficial lap record for Superstocks and the SMT Bathams BMW rider will hope to add to his 13 wins at the meeting.
He was followed in by Seeley (121.40) and fellow Englishman Hutchinson (120.80).
Somerset's Jessop boosted his hopes of a maiden NW 200 success with a pacesetting 107.34 in the Supertwins, edging out Ivan Lintin (107.33) with Ryan Farquhar (106.78) third.
Remaining North West 200 practice and race schedule
Thursday 12 May - Roads close from 09:15 to 15:00 for practicing and 17:00 to 21:00 for racing
Race 1 - Supersport (6 laps); Race 2 - Supertwins (4 laps); Race 3 - Superstock (6 laps)
Saturday 14 May - Roads close from 09:30 to 19:00 for racing
Race 1 - Supersport (6 laps); Race 2 - Superbike (7 laps); Race 3 - Supertwins (4 laps); Race 4 - Superstock (6 laps); Race 5 - NW200 Superbike (7 laps)