Larry Herndon hit a fourth-inning two-run homer and Juan Berenguer and Aurelio Lopez combined on a seven-hitter as the Detroit Tigers defeated the Kansas City Royals, 4-1, yesterday at Detroit.

Then the Tigers won the completion of a suspended game, 10-1.

The first game marked the return of George Brett's bat from the American League office following league President Lee MacPhail's ruling reversing the umpires' decision and validating Brett's home run last Sunday against the Yankees.

However, Brett went 0 for 3. He fouled out to catcher John Wockenfuss in the first inning and later flied out twice.

Following the regular game, the two teams completed Friday night's game which was suspended after eight innings because of a local curfew law. The final score was the score of the game when it was stopped. Jack Morris (11-8) was the winning pitcher. Larry Gura (8-15) was the loser.

In the regular game, the Royals took a 1-0 lead when Pat Sheridan hit the first pitch from Berenguer (5-2) into the upper right field seats for a leadoff homer.

Enos Cabell doubled in the Tigers fourth and went home on Herndon's 12th home run of the season--a shot into the lower left field stands on a 1-0 pitch from Bud Black (4-4).

Marty Castillo's bases-loaded single off Black in the eighth scored the other two runs.

Berenguer, who struck out a career-high 10, worked the first seven innings, giving up seven hits. Lopez worked the last two innings and got his 15th save.

"I watched the Royals last night from the bench and studied them," said Berrenguer, who played part of the 1981 season for Kansas City. "I know some of them, still . . . (Today) I felt nobody could hit me because I had a good fast ball and slider."

Brett's bat was delivered to Tiger Stadium about two hours before the start of the 2:15 p.m. game. It was shipped to Detroit Friday, after spending the week in the league's New York City headquarters.