Lehigh (8-0, 2-0) never trailed, scoring first when Laquan Lambert returned a blocked punt 60 yards for the touchdown.
Young rushed 23 times for 100 yards.
After two more rushing touchdowns by Young in the third quarter cut Lehigh’s lead to 21-19, Colvin responded.
Colvin rushed for two touchdowns in the second half, sparking Lehigh’s run. The Mountain Hawks finished the game scoring 21 unanswered points.
Colvin finished 20 of 32 for 298 yards, three touchdowns and two interceptions.
Lehigh has won 16 straight regular-season games and has beaten Bucknell the last 15 times.