Byron Fulton contributed 13 points and 10 rebounds off the bench for the Wildcats (19-4 overall, 11-1 Big Sky), who beat the Lumberjacks for the eighth straight time.
Durrell Norman scored 11 points for Northern Arizona (5-20, 1-12), which has lost 12 straight, its longest losing skid in 23 years.
Lillard, the nation's leading scorer at 25.5 points per game, scored seven straight points to put Weber State up 28-14 with 4:23 left in the first half.
Northern Arizona closed the gap to 30-23 with back-to-back 3-pointers right before halftime and then cut the deficit to five early in the second half. But the Wildcats quickly regained a double-digit lead courtesy of Bullinger, who scored Weber State's first 10 points of the second half.