Through its 114-year history, Harley-Davidson has taken on numerous contenders intent on dethroning it as the dominant American motorcycle maker. So far, it has a perfect record.

But Harley now faces perhaps its most trying challenge in decades. Polaris, an established American company with manufacturing know-how and a revered motorcycle brand in Indian, is quickly making big strides.

Polaris surprised the industry in January when it announced that it would shut its homegrown motorcycle brand, Victory, and focus entirely on Indian, a company it bought in 2011. So far, the move seems like a smart one.

Indian’s sales grew 17 percent in the second quarter of this year, while Harley’s sales shrank nearly 7 percent. Overall sales for large-displacement bikes, the kind that Harley specializes in, shrank 9 percent in the second quarter of this year.