Al Bumbry went to camp today and talked to a bunch of demanding youngsters. "The kids asked for a home run," said Ken Singleton. "He said, 'How about two singles?' They said, 'Nope, a homer.' "

Kids are picky these days. They want instant gratification. Bumbry gave it to them with a two-run homer, his second of the year and his second off loser Jim Beattie, and the Orioles beat the Seattle Mariners tonight, 3-2.

"They were in the upper deck," he said. " . . . So as I was running around the bases, I thought of them and waved. "

If they were looking for good omens at the start of the second half of the season, and ballplayers almost always do, the Orioles could have found them tonight. Scott McGregor, who started the season 0-2, won his 11th game to tie LaMarr Hoyt of the White Sox for the league lead. And Sammy Stewart, who has been pitching in Class A Hagerstown for three weeks, rehabilitating his sore knees, got his second save.

Stewart, who was reactivated before the game (with reliever Don Stanhouse placed on waivers to make room) and pitched for the first time since June 22, came on in the seventh with two outs, two on, and two runs in. He got ahead of Rick Sweet 1-2, and was walking off the mound nonchalantly before Bumbry caught the fly ball in center field.

It may not have been the most graceful game, but it was the kind the Orioles must win and have not been winning, the kind Manager Earl Weaver said "could have been blown." They are now 7-12 in one-run games, the Mariners' specialty (20-13).

Coming from behind is another Mariner specialty. They did in the Orioles twice that way last week in their Kingdome kingdom. But not tonight. The Orioles scored their first run in the second. Eddie Murray and John Lowenstein singled and the rains came. Twenty-five minutes later, Cal Ripken Jr. struck out before Dan Ford swung protectively and meekly at an 0-2 pitch and hit a knuckler down the right field line for an RBI single.

The Orioles' second and third runs were more definitive. Lenn Sakata singled and Bumbry impressed his young friends with an opposite-field home run. It was a 1-0 pitch. "Kind of a slider," Beattie called it.

And so it remained 3-0 until the seventh. McGregor was simply unyielding. He gave up only one hit in the first six innings, and that, a double by Dave Henderson to left, could have been caught. He threw 77 pitches before he left, only 24 balls.

In the seventh, he relented a bit. "The weather didn't get to me," he said, "the bats did."

There were two outs. Al Cowens and Richie Zisk singled to left. Henderson walked, loading the bases, on a 3-2 pitch.

Todd Cruz was next. McGregor, who had been throwing him change ups, threw one too many. Then again, he had given up four home runs in four games on fast balls. The change up it was, and Cruz singled to left scoring two runs. "I thought I had him set up for the pitch," McGregor said. "I was too timid to throw it."

In came Stewart. He was nervous, but it didn't show. He had gotten to the park 20 minutes earlier than usual. Partly because he couldn't wait and partly because of all the things he has to do to protect his knees from their tendinitis: ultrasound, deep heat, braces and lots of talcum powder so the braces don't scratch. He has been living with the condition since high school. His right leg is a half-inch shorter than the left; he says, "Lots of guys from North Carolina have one leg shorter than the other from climbing too many mountains."

So he never thought about it until his knees forced him to, on June 22 in Cleveland, when he lasted only 1 2/3 innings while starting. This was a lot better, retiring all seven men he faced. "We missed it," Weaver said.

No more than Stewart. He was satisfied, to be sure. "But I won't be finished until I get my picture on the cornflake box," he said.