The American was the only one of the three joint leaders to go out early, with Jordan Spieth and Brooks Koepka, who also shot five-under par on Thursday, due out in the afternoon.
Most of the early starters found conditions difficult, with swirling winds and cold conditions.
Kuchar dropped a shot at the second but then picked up his game spectacularly, with a chip in for a birdie at the third, when he seemed in danger of dropping another shot, and following up with another birdie at the par-three fourth, to grab the outright lead.
With the wind expected to pick up throughout the day, a good start was vital and Kuchar's early draw could prove a real advantage.
Elsewhere, Paul Casey sported special shoes to mark his 40th birthday but had little to celebrate after dropping two shots in the first three holes.
The Englishman started the day just one shot off the joint leaders after his first-round 66, but soon found trouble on the second hole, with a wild drive and poor second shot into the bunker.
After missing his par, Casey went on to drop another shot at the next hole when he skirted a short putt past the hole.
It was enough to forget any thoughts of a happy birthday, despite the fetching blue-and-white shoes which had PC and 40 stitched into their back.
Masters champion Sergio Garcia had trouble of a different sort, appearing to strain his wrist chipping in off the green and asking for a physio to meet him on the course.
(Reporting by Neil Robinson; editing by Sudipto Ganguly)
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