Thirteen-times North-West 200 winner Michael Rutter posted the best Superbike time in Tuesday's opening practice session.
The 42-year-old's best average lap speed was 121.106mph, just ahead of British Supersport Championship star Alastair Seeley who clocked 120.383.
William Dunlop posted the best time in the Supersport with Scotsman Keith Amor the best in the Supertwins class.
Austrian Horst Saiger was the surprise name at the top of the Superstock.
There will be further practice sessions on Thursday morning and the races get underway that night with Supersport, Supertwin and Superstock events.
Nine of Rutter's 13 victories at the Triangle circuit have been in the Superbike class.
The former MotoGP and World Superbike rider signalled he is capable of making double figures by edging Carrickfergus man Seeley in the first practice run.
William Dunlop, keen to make an impression in the colours of Tyco Suzuki, claimed provisional pole in the Supersport category ahead of Rutter and Seeley.
However, Rutter was delighted with his opening practice runs.
"It is a really nice way to start things off and although we have a few little issues to resolve all the bikes are going really well," said the Birmingham rider.
Michael Dunlop endured some early teething problems during the opening Superbike session but appears confident that there is much more to come from his BMW.
"We are waiting for an electronics man to arrive to get some settings sorted. We aren't really riding the bike yet," said Dunlop.
Carrickfergus man Seeley has still to post a qualifying time in the Superstock category but managed top-three placings in both the Superbike and Supersport listings.
"I could have done with another couple of laps on the 600 and I did my fastest lap on the Superbike on a tyre that I didn't really like but we are not far away with any of the bikes," said Seeley.
Amor unofficially blitzed James Hillier's Supertwin lap record on the KMR Kawasaki as he took pole ahead of team boss Ryan Farquhar and young team-mate Conor Behan.
"I had to learn my way around again," said Scot Amor at his first North West in five years.
"It is so fast here and a bit scary but I really enjoyed being back.
"I am under no illusions, I know that the twins races will be dogfights but I am looking forward to them."
Macau Grand Prix winner, Ian Hutchinson, having his first UK road race ride since 2012, crashed out of the Supersport practice at Mill Road roundabout on his Milwaukee Yamaha R6.
Hutchinson was taken to hospital with an injured finger but made his way back to the track for an outing on his superbike during the final Superstock practice.
Tuesday's top practice times
William Dunlop (Tyco Suzuki) 114.754
Michael Rutter (Smiths Triumph) 114.193
Alastair Seeley (Mar-Train Racing Yamaha) 114.177
Michael Rutter (Bathams BMW) 121.106
Alastair Seeley (Mar-Train Kawasaki) 120.383
Guy Martin (Tyco Suzuki)
Keith Amor (KMR Kawasaki) 106.60
Ryan Farquhar (KMR Kawasaki) 106.06
Connor Behan (KMR Kawasaki) 106.04
Horst Saiger (Kawasaki) 118.54
Michael Rutter (Bathams BMW) 118.49
Stephen Thompson (Bathams BMW) 118.41