It took both the quickness of a sprinter and the heart of a marathoner, but the Los Angeles Lakers crossed the finish line Tuesday night at the Forum with history borne triumphantly on their shoulders and brazen guarantees safely tucked away in their memories.

With James Worthy carrying the baton in Game 7, the Lakers outdistanced the Detroit Pistons, 108-105, to become the first team since the Boston Celtics in 1969 to repeat as champions of the National Basketball Association. Worthy, voted the most valuable player of the series, chose this night to have the first triple-double of his career - 36 points, 16 rebounds and 10 assists - bringing the Lakers to what may be the end of their championship ring cycle, with five rings in the '80s."I don't have any feelings left just now; I feel raw for them," said Laker Coach Pat Riley, who had pledged the Lakers to another title within a half-hour of the team's championship victory over the Boston Celtics in 1987.

"At the end of the game, what were we doing? We were watching a great basketball team hold on. We were holding on, and we had a big enough lead to do so," Riley added.

But barely. The Lakers, who had burst ahead of the Pistons by making their first 10 shots of a third quarter, which began with Detroit ahead by five and ended with the Lakers up by 10, nearly had a 15-point lead expire in the last 7:27.

Detroit, which limped into the game with Isiah Thomas playing on one good leg, pulled to within one point, 106-105, on Bill Laimbeer's three-point basket with six seconds left. But Magic Johnson, who had 19 points and 14 assists, spotted A.C. Green for the breakaway layup that finished off the Pistons and completed what Johnson called the most difficult season of his life.

Riley had better not make any more pledges within earshot of Johnson.

"I just hope I don't see him on vacation again this summer," said Johnson, who had bumped into Riley on a beach in the Bahamas a year ago.

Michael Cooper, who incinerated his shooting slump with 12 points, including two three-pointers, was even more emphatic about Riley not setting any future tasks for this team.

"If he says anything like that," Cooper said, "I'll stick my fist so far down his throat he won't be able to talk for a week."

For a time, the Pistons placed a heavy boot on Laker necks, taking a 52-47 halftime lead as Kareem Abdul-Jabbar went scoreless, Byron Scott had just five points, Cooper was 0 for 4 from three-point land and Magic Johnson had as many turnovers (three) as baskets.

Thomas, meantime, a doubtful starter who was still on crutches when he arrived at the Forum Tuesday afternoon, had 10 points and four steals by the intermission, having dribbled unchallenged down the floor for the basket that gave Detroit its five-point advantage.

"We wanted to stop throwing the ball away," Johnson said. "We had 11 turnovers in the first half; we'd been averaging 11 a game.

"We wanted to establish our game in the first three minutes (if the third quarter). Let them know, `We're here.' "

Scott was the first one to go calling, throwing down a thunderous dunk over Piston center Laimbeer on the break. That triggered a succession of Laker relays downcourt, with Worthy scoring seven straight points and Scott pouring in 11, including a three-pointer that finished off a 23-7 Laker run and gave Los Angeles a 70-59 lead.

The Lakers didn't miss a shot in the period until Scott threw up an airball with 5:05 left.

"They seized the game with their ferocious defense," Detroit Coach Chuck Daly said.

But the Pistons made a last grab to get it back, with both Thomas and Adrian Dantley on the bench, in the last seven minutes.

"I don't even know what happened in the last minute, minute and a half," Riley said. "I was just holding on."

The mouth of Motown, Piston forward John Salley, showed he had the mettle to match his wit with 10 points in the final period, most of them coming in heavy traffic.

In a four-minute span, Detroit sliced 13 points off its deficit, outscoring the Lakers, 17-4, to pull within two, 98-96, after Laimbeer blocked a pass by Abdul-Jabbar and sent Dennis Rodman away for an easy layup.

Magic Johnson missed a spinning layup attempt, but Worthy tipped once, then twice before getting the ball to drop. Vinnie Johnson answered with a jumper to make it a two-point game again. After a pair of free throws by Magic, Laimbeer dived to the floor to save a loose ball, with Dumars converting that save into a jumper that cut the Laker margin to 102-100 with 1:18 left.

It was still a three-point game when Laimbeer blocked a shot by Worthy, but Rodman elected to pull up for a jumper on the break, a decision that had Daly going crazy on the Piston bench. The shot bounced off, Scott rebounded and then made two free throws with 30 seconds left.

That should have been enough, but Cooper missed two free throws, and Dumars scored to make it 105-102 with 16 seconds left. With 14 seconds to go, Worthy was fouled, but he made just one, and Laimbeer's three-pointer made it a one-point game with six seconds left.

Johnson, however, put a stop to the mounting hysteria right there with his court-length pass to Green.