Harley-Davidson Inc.'s main ad agency for more than three decades is dropping the struggling motorcycle maker in favor of new business.

Ad agency Carmichael Lynch, a unit of Interpublic Group, says many factors went into the decision, including the fact that the Milwaukee-based motorcycle maker has slashed its marketing spending in recent years amid slumping sales.

Carmichael Lynch President Doug Spong says the motorcycle company was also never a big spender on traditional advertising.

According to Kantar Media, Harley-Davidson spent about $11 million on television ads and other measured media last year.

Harley-Davidson says it has a big roster of ad agencies. Chief Marketing Officer Hans Richer says the company feels good about its creative direction.