Im Sung-jae and Chad Ramey hit rounds of six-under 65 to move into the lead by one shot from last week's Sanderson Farms Championship winner Sam Burns at the halfway point at the Shriners Children's Open.
Day one leader Kang Sung-hoon had a forgettable second round, carding a two-over 73 to slip six shots off the pace at the TPC at Summerlin in Nevada on Friday.
Countryman Im, currently ranked 29th in the world, carded six birdies across his round, including finishing off a birdie on the par-five ninth. Im's bogey-free first two rounds mark the best opening 36-hole score in his PGA Tour career.
American Ramey, who is making only his fifth start in his PGA Tour career, had seven birdies along with a bogey on the first, with the pair level on 14 under after two days.
Burns looms one stroke behind the joint leaders on 13 under, with the 18th-ranked American backing up his opening round of 66, with an eight-under 63.
“What we tried to do is just last week is last week,” Burns told reporters following last week's triumph in Mississippi.
"This week is Shriners and preparing for this week, trying to make sure Monday, Tuesday, Wednesday that we are giving ourselves the best opportunity to play well this week. Obviously, incredible honoured that I won last week and such a fun time, but just trying to kind of leave that there.”
The 25-year-old carded five birdies on his back nine, including a 132-yard wedge which landed within three feet for birdie on the sixth hole.
Burns is joined by Adam Schenk after he carded a six-under 65, with Aaron Wise a stroke behind the duo at 12 under at the halfway mark.
Four-time major winner Brooks Koepka remains in contention after a four-under 67, leaving him seven under.
Ryder Cup debutant Scottie Scheffler and Patrick Reed were among those to miss the cut, while Rickie Fowler along with last week's Sanderson Farms Championship contenders Cameron Burns and Sahith Theegala all missed the cut by a stroke.