Kuchar notched seven birdies and no bogeys at Riviera Country Club in Palisades, Calif.
Sergio Garcia carded a 6-under 65 to ending the day alone in second place.
Brandt Jobe fired a 66 for third place.
Rookie James Hahn, David Lynn and Charlie Beljan each carded a 4-under 67 to share fourth place before play was suspended.
Selena Gomez drops F-bomb, walks off stage during Jingle Ball performance
Trader Joe's: Car crashes into Long Island store, injuring 11