"I don't know about any hexes," said Royals third baseman George Brett after the New York Yankees defeated Kansas City, 6-2, yesterday in Yankee Stadium. "But I do know we can't seem to hit and score runs here . . . I can't explain it."

The Royals last beat the Yankees in New York Aug. 18, 1983, the infamous "pine-tar" game in which Brett's ninth-inning home run won for the Royals, 5-4. Since, they have lost nine in a row at Yankee Stadium, scoring only 11 runs in the nine games and never more than two runs in a game.

The Yankees, sweeping the weekend series, 7-1, 5-2, 6-2, for a four-game winning streak since losing their first two outings under reinstituted Manager Billy Martin, broke out with four home runs yesterday. They included fifth-inning back-to-back shots by Rickey Henderson and Don Mattingly. Both drives off Bud Black (2-2) carried well beyond 400 feet.

"There is no doubt about the pop in our lineup," Mattingly said. "Most of the guys who weren't hitting early, Winnie (Dave Winfield) and me, missed time in spring training with injuries. Now we're getting our at bats."

Dale Berra started the winning rally with a single and slid hard into Frank White as the second baseman tried to turn Billy Sample's grounder to third into a double play. Sample was safe at first and, an out later, scored on Henderson's second homer this season, into the left field seats, breaking a 1-1 tie. Mattingly then reached the right field stands, giving right-hander Phil Niekro (4-2) all the runs he would need.

Niekro pitched 7 1/3 innings, giving up four hits, striking out four and walking six before leaving with a cramp in his upper right forearm. Dave Righetti finished for his seventh save.

Sample had given the Yankees a lead in the third inning by hitting his first homer. Steve Balboni made it 1-1 in the fifth with his sixth homer of the season. Ken Griffey, hitting for Sample in the sixth, homered with none on off Joe Beckwith.