Shares of Harley-Davidson have revved up some nice gains in the past year.

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NEW YORK (CNN/Money) - Vroom vroom!

That's not just the sound a Harley-Davidson motorcycle makes when you rev up its signature engine. It's also the sound of Harley's soaring stock price.

Harley (Research) surged nearly 30 percent last year and the stock is currently trading about 6 percent off its 52 week-high. So with the company set to report its fourth quarter results on Thursday, investors and hog aficionados have to be wondering if the shares have more room to run.

Analysts are forecasting a pretty solid quarter for the company, with sales expected to rise 6 percent from a year ago to $1.22 billion and earnings expected to increase 14 percent to 69 cents a share.

And these numbers might be a little low. According to figures from the Motorcycle Industry Council, on-highway motorcycle sales increased 15 percent in December.

In light of this data, Ed Aaron, an analyst with RBC Capital Markets, said that it looks like Harley retail sales in December were probably very strong, despite the fact that the winter months are typically a slower seasonal period for motorcycle sales.

But the question now is just how strong 2005 will be for Harley. Jake Balzer, an analyst with Guzman & Co., said that there are some concerns about growth slowing for the company.

To that end, analysts are predicting a 13 percent rise in profits in 2005 and gains of about 15.5 percent annually for the next five years compared to an expected increase of 19 percent in 2004.

Balzer said the primary reason for a more tempered growth outlook is demographics, namely that its core group of customers is aging and will be unlikely to buy as much as they have in the past few years.

But Balzer said he thinks the stock, trading at about 18 times 2005 earnings estimates, is attractive given the company's impressive track record. And it's not as if Harley hasn't faced the problem of needing to attract new customers before. The company, after all, is more than 100 years old.

"Harley has outgrown its core market in the past. But the company does a good job of updating the models and keeping riders excited," said Balzer.

Along those lines, Tim Edwards, an analyst with the Henssler Equity fund, which owns shares of Harley, sees some encouraging signs for the future.

He points out that one of the best selling Harley model for the past few years is its Sportster. And although this is a cheaper bike that is geared more toward Harley newbies, Edwards said that robust Sportster sales could lead to a pickup in higher-priced models in the future, such as the Softail, which can cost upwards of $20,000.

"The potential exists for people buying the Sportster now to trade up to a higher margin product. Typically, Harley owners do trade up to more profitable bikes," said Edwards.

Still, Edwards has some doubts about profit margins in the short-term, which could weigh on the stock. Specifically, he said that he's a bit worried about the company's use of financing incentives at the end of last year to spur demand.

"A lot more bikes are selling at MSRP so Harley is starting to give the appearance of being more like auto companies, using incentives to push product through the dealer," Edwards said. "That could boost unit sales but at what cost?"

However, Harley has faced concerns about its financing division before. Short-sellers have often targeted the stock because they have felt that Harley's profits were juiced by accounting gains in the finance division.

But Kent Mergler, president of Northstar Capital Management, an institutional firm that owns shares of Harley said worries about how much profit Harley makes from financing as opposed to selling the actual bikes are overblown given how costly many of the company's products are.

"When you are selling a $20,000 item, it's not unusual to have financing arm," said Mergler. In addition, operating profits from Harley's financing division accounted for just 14 percent of total operating income in the third quarter.

When push comes to shove, the case for Harley is a pretty simple one, RBC's Aaron said. "Harley has a very strong brand name and very high earnings visibility," he said.

And Mergler said he's not worried about any short-term bumps the company may face.

"This is a core holding type of stock. You get these noises from time to time in the short-term but Harley has never really disappointed. Fundamentally, the company just cranks it out," he said.

Analysts quoted in this story do not own shares of Harley-Davidson and their firms have no investment banking ties to the company.