Being able to switch quickly from cruiser to touring bike with fast-release saddlebags and windshield should make Polaris Industries' new Indian Springfield a popular choice. Image source: Indian Motorcycle.

It's been a long, long time since Harley-Davidson (HOG -0.06%) has had serious competition in the American-made big-bike market, but Polaris Industries (PII 0.63%) is beginning to give it a real run for its money, with the new Springfield edition of its Indian Motorcycle nameplate just the latest to gun its engines.

Harley still owns almost half of the U.S. motorcycle industry, but it can no longer afford to ignore its rival. The slippage it's seeing in sales and shipments is a direct testament to the successful reintroduction Polaris achieved with the Indian brand. And up and down the model lineup, it is showing it is quite capable of going toe to toe with Harley-Davidson.

The Indian Springfield is now taking aim squarely at the Road King, the heart of Harley's touring bike segment. That's important: Of the more than 266,000 bikes Harley-Davidson shipped in 2015, fully 43% of them were touring models, and that's actually down from the year before, when they accounted for 45% of the total. Its cruiser shipments were down as well last year, and it's no coincidence that Polaris just introduced the Chief Vintage, Chief Classic, and Chieftain models. With more than three-quarters of Harley's bike sales in these two divisions, another model that could swipe even more sales is troubling.

And the Springfield may be even more of a headache because it's flexible enough to ride between both segments, with quick-detach windshields and removable saddlebags that allow riders to shift easily between cruiser and touring. The bags and the handlebars are both remote-locking.  It should be a bike that appeals to a broader range of customers than usual for Indian, and indicates that Polaris wants to compete across the board.

It has a big hole to drive through to do so, too. When Harley-Davidson reported fourth-quarter earnings back in January, it noted it was targeting its new outreach customers more than its core customers. It wants the outreach group to grow faster than the core, and it appears to be having some success: Outreach customer growth hit 6.5%, ahead of its core base and double the rate of industry growth.

That lack of attention to what has traditionally been Harley's bread-and-butter customer gives Polaris an opening, and if its sales are any indication -- motorcycle revenues were up 67% in 2015 even as Harley-Davidson's sales fell 6% -- it's taking it.

Targeting the same niche as the Road King, Polaris Industries Springfield could give Harley-Davidson a run for its money. Image source: Indian Motorcycles.

Named after the birthplace of the original Indian Motorcycle company, the Springfield comes equipped with the same Thunder Stroke 111-inch, 1,811-cc engine that Indian puts in its similar-class bikes like the Chieftain and Roadmaster models, and with a starting price just under $21,000, it's priced above the Chief Vintage but below the Chieftain.

It comes after Indian introduced the Scout Sixty, the lowest-priced model the bike maker offers, which, at under $9,000, is targeted toward the same new riders Harley is going after with its Street 500 and 750 models. The Springfield, though, is a feature-rich bike, and comes with options like heated driver and passenger seats, soft lowers, a 17-gallon accessory trunk, and heated grips. Its versatility makes it a vehicle that could appeal to new riders wanting a heavyweight bike, riders who may have previously considered a Harley Road King, which starts at under $19,000.

Polaris now has bikes all across the size and price spectrum, and ought to take even more share of the market with the latest introduction. Even so, it sold just nearly $700 million worth of motorcycles last year, and that includes its Victory brand and the Slingshot three-wheeler. Harley-Davidson, on the other hand, sold more than $4.1 billion worth of bikes. Polaris and the Indian nameplate still have a long way to go.

Sure, Milwaukee-based Harley may be stumbling a little as bike buyer dynamics change, but it shouldn't be counted out. Of course, that doesn't mean motorcycle enthusiasts can't still enjoy seeing a vibrant market develop for heavyweight bikes, particularly if it comes with the styling and heritage of an Indian.