LA QUINTA, 24 Jan, 2015 (AFP) - Kuchar, who began on the back nine, rolled in four birdies on one five-hole stretch beginning at No. 12 and has a one-shot lead over Michael Putnam after the second round of the $5.7 million event. Kuchar is at 15-under 129 for 36 holes.
Palmer appeared at one point to be headed for a 59 but ended with a record-tying 11-under 61. He is tied for seventh with three others after his spectacular round on the Jack Nicklaus Private Course at PGA West in the California desert.
Over the first three rounds, players will alternate between playing the Arnold Palmer and Jack Nicklaus Private Course, along with the La Quinta course. Sunday's final round will take place on the Palmer Course.
Kuchar played his final five holes at even par, making his first and only bogey on number six to go along with another birdie on the eighth.
"Today was better even than yesterday," said Kuchar, a seven-time winner on the PGA Tour and coming off a tie for third at the Sony Open in Hawaii last week.
"I had a nice round over at La Quinta and that may be the toughest of the three courses -- just how tight and narrow it is. (Nicklaus Course) you have a little more space and reachable par-fives."
First-round leader Putnam carded a five-under 67 and is tied for second with 2010 champion Bill Haas (63).
Justin Thomas (63), Nick Watney (64) and Scott Pinckney (67), all of whom played the Nicklaus Course Friday, are tied for fourth at 13-under 131.
Defending champion Patrick Reed finished his second round tied for 22nd at nine-under 135 after shooting a two-under 70.
Palmer, who started on the back nine, began the day at one-under and eight shots back, but he quickly moved up the leaderboard.
After an eagle on 12, Palmer tallied three straight birdies from 13 and followed those up with another eagle on the par-five 16th. Palmer kept rolling with another trio of birdies on 17, 18 and one.
Palmer's quest for a 59 included birdies on number four and six. Heading to the par-five eighth, Palmer needed to finish eagle-birdie to shoot 59. He birdied eight and then made par on the ninth when his birdie putt rolled by the hole.
Leading second-round scores on Friday in the US PGA Tour's $5.7 million Humana Challenge (USA unless noted, par-72):
129 - Matt Kuchar 65-64
130 - Bill Haas 67-63, Michael Putnam 63-67
131 - Nick Watney 67-64, Justin Thomas 68-63, Scott Pinckney 64-67
132 - Alex Cejka (GER) 68-64, Erik Compton 66-66, Ryan Palmer 71-61, Steve Wheatcroft 65-67
133 - Martin Flores 68-65, Jason Kokrak 65-68, Nick Taylor (CAN) 66-67
134 - J.J. Henry 67-67, Pat Perez 66-68, Steven Alker (NZL) 68-66, Charley Hoffman 71-63, Brendon de Jonge (ZIM) 69-65, Martin Laird (SCO) 68-66, James Hahn 67-67, John Peterson 64-70