Yin and Kim share LPGA LA Open lead after seventh round
Yin, 20, teed off on the 10th at Palos Verdes Golf Club and was three-under through her first eight holes.
She picked up four birdies in a five-hole stretch, including three straight at the fifth, sixth and seventh on the way to a 10-under par total of 132.
Kim, whose five LPGA titles include a major at the 2014 Evian Championship, carded her second straight 66, posting five birdies without a bogey.
Yin, playing the second event of her second LPGA campaign, was impressive on the greens, needing just 24 putts.
She had seven straight one-putts on the first through seventh holes, but she said the real key to her round was ball-striking.
"I felt my game was in a pretty solid spot right now. I can strike the ball well and my approach shot is pretty good," she said.
"Last year I only play fade with every shot. This off-season I was working on maybe hitting a little draw, and I think that works," she said.
Kim had two birdies on the front nine and three coming in, taking advantage of all three par-fives.
But she said avoiding a bogey was key.
"There were a couple situations actually where I could have carded a bogey, but in those instances my putter worked well," she said.
The leading duo were one stroke in front of Japan's defending champion Nasa Hataoka, who posted a 66. Canadian Maude-Aimee Leblanc was in fourth on 134 after a second straight 67.
South Korean Lee Mi-hyang, the Monday qualifier who led after the first round, slipped seven shots off the pace with a three-over par 74.