PITTSBURGH -- Delwyn Young waited a long time just to drive in a run. So getting four RBI may have been worth the wait.
"I haven't driven a run in it seems like six months," Young said, "so just to get one -- let alone four -- is a good feeling."
Paul Maholm allowed only two runs in seven innings and Jack Wilson and Adam LaRoche each had two hits and an RBI for Pittsburgh, which clinched a winning record in interleague play for only the second season since the format was adopted 12 years ago.
Willie Bloomquist had two hits and scored twice, and Billy Butler had two RBI singles for the Royals, who got an effective start from Bruce Chen, making his first major league appearance in more than two years.
Kansas City (31-42) fell to a season-low 11 games under .500.
Young, usually a reserve, had his last RBI on June 11 and had only two this month and four total since May 18.
He has hit safely in nine of his past 11 starts and is hitting .346 when in the lineup. Young is pushing Brandon Moss for playing time in right field but also has starts at second base and left field.
"Delwyn had a great night tonight. He's played well for us," Pirates manager John Russell said. "It's nice to have that with Brandon and Eric [Hinske] and Delwyn as options out there. We're pretty solid in right field. [Young has] continued to do whatever we've asked of him. It's a good problem to have."
Maholm (5-4) entered the game with the best home ERA in the NL, a number that climbed to 1.96 after his strong outing. Making his first start of the month at PNC Park, Maholm allowed only five hits and a walk, winning for only the second time since April 22.
He is 22-12 in his career at home; 13-27 on the road.
"I couldn't tell you why," Maholm said. "I feel good on the road, too. Apparently, that just doesn't translate there. I don't know if it's a comfort thing? You go out there and you're in your normal routine, just go out there and expect to win."
Young's homer -- his second of the season and fifth of his career -- was to straightaway center with Freddy Sanchez and LaRoche aboard in the fourth. That put the Pirates ahead to stay, 3-2.
"I was looking for a fastball, and it was a changeup, so I sat there and was able to get good wood on it and it was able to go," Young said. "I didn't think it was going to leave, but it did."
He added an RBI single in the eighth.
Butler drove in Bloomquist with RBI singles twice during the first three innings. Each time, Bloomquist's speed helped set it up. He hit his fifth triple in the first and stole his 13th base in the third.
Wilson gave Pittsburgh an insurance run in the seventh when his two-out single drove in Andy LaRoche, who had tripled.
Adam LaRoche added an RBI single in the eighth.
Making his first appearance since April 20, 2007, and first start since Aug. 4, 2006, Chen (0-1) allowed seven baserunners and faced only four over the minimum through six innings.
The lefthander, who had Tommy John surgery on his elbow two years ago, would be charged with four runs on seven hits with no walks and two strikeouts.
"I didn't think Chen was that bad," Royals manager Trey Hillman said. "He left that pitch up for the home run, but I thought he pitched effectively on both sides of the plate. He mixed in a couple different breaking balls. His command of the ball, all were good."
The left-hander, who had Tommy John surgery on his elbow two years ago, allowed four runs on seven hits with no walks and two strikeouts.
"You have surgery at 31 years old, you don't know what's going to happen," Chen said. "You sign March 1, very late. At that point, I didn't know. I'm very glad I was able to get an opportunity, and here I am back. I'm very grateful."
Pittsburgh is 8-6 against the American League with Sunday's game the final interleague contest of the season. The Pirates, worst in the majors at 71-109 against the AL, went 8-7 against the AL in 2001. ... The Pirates won their 10th in a row when playing in front of home crowds of at least 20,000 and are 11-1 overall in those games. The attendance on fireworks night was 36,032. ... Chen -- who appeared in a game for his 10th different team -- had a single, his first hit since May 21, 2006. ... For the second consecutive game, each team wore replica Negro League uniforms.