Harley-Davidson’s stock got clobbered on fears that its core customers are getting too old to ride bikes, even as Trump’s tariffs continue to tank profits.

US sales, which account for roughly half of Harley’s business, tumbled 10.1 percent from a year earlier, stoking concerns on Wall Street that millennials aren’t interested in the company’s pricey motorcycles.

Harley’s profits have likewise gotten slammed by tariffs on steel and aluminum levied by President Trump, who said last year he’d back a boycott of the company as punishment for moving production overseas.

On Tuesday, Harley management said it expects the tariffs to cost as much as $120 million in 2019.

Shares of the Milwaukee-based motorcycle-maker plunged more than 9 percent at Tuesday’s open after reporting weak quarterly sales. Harley’s stock recouped some of its losses to close down 5.1 percent at $34.76.

Harley is struggling to attract younger riders as its core baby boomer customers increasingly hang up their boots.

“Demographics are working against them,” Felicia Hendrix, analyst at Barclay’s told The Post.

Harley unveiled its first electric bike — the LiveWire — earlier this year in a bid to attract new and younger riders.

But the LiveWire, which is set to go on sale in August, has drawn scorn for its lofty price tag. At just under $30,000, the LiveWire costs more than an entry-level Toyota Prius.

“You need to give millennials some entry into the brand,” Hendrix said.

Harley acknowledged the troubles it faces while trying to stay upbeat.

“While we expect our business to remain under pressure in 2019 driven by continuing challenges in the US motorcycle industry, we intend to introduce exciting new products and add innovation,” financial chief John Olin said on a call with analysts Tuesday.

Adjusted fourth-quarter profits were 17 cents per share — well below the 28 cents expected by analysts surveyed by Refinitiv.

When adding in tariff and restructuring costs, profits were zero per share for the quarter. Global sales were down 6.7 percent.