Harley-Davidson will pay $12 million for selling a device that enabled its iconic motorcycles to go faster while spewing more harmful pollutants, the Environmental Protection Agency said Thursday.

“This settlement immediately stops the sale of illegal aftermarket defeat devices used on public roads that threaten the air we breathe,” said Cynthia Giles, EPA’s enforcement chief. Under the agreement, she said Harley-Davidson is taking “important steps to buy back the ‘super tuners’ from their dealers and destroy them, while funding projects to mitigate the pollution they caused.”