Wells Fargo downgraded Harley-Davidson on Monday to a neutral rating, citing a persistently weak market for large motorcycles, uncertainty over tariffs and a "long path to stabilization."

Though the iconic American bike maker has embarked on an ambitious plan to revamp its product line and attract new riders, a number of voices on Wall Street still think Harley-Davidson has a lot of work ahead of it in a fundamentally changing landscape.

Much of Harley-Davidson's customer base is older, and younger buyers are less interested in the big, brash motorcycles the company specializes in. Younger buyers tend to favor smaller motorcycles, and often tend to be interested in motorcycles for practical benefits such as ease of ownership and fuel costs, rather than as lifestyle purchases.

Harley also faces competition from the likes of Polaris's Indian brand, among others.

"As demographics and consumer preferences shift, large heavyweight motorcycles, regardless of brand, remain challenged," said Wells Fargo analyst Timothy Conder in a note Monday. "We believe HOG's plans for mid/small bikes, growing ridership, bringing in younger demographics to the brand and international expansion (led by Asia), collectively should provide meaningful growth opportunity over time."

Shares of Harley-Davidson were down nearly 1% Monday afternoon. The stock has risen by 16.85% since the beginning of the year.

Tariffs are also a concern, though Harley-Davidson has tried to protect itself from risks emerging from an ongoing international trade war. The company is shifting production bikes meant for the European Union to Thailand, in order to guard against E.U. tariffs on U.S. made motorcycles. But there is a risk of tariffs on any motorcycle imports to Europe, regardless of where they are made, Conder said.