Turns out that the use of so-called “defeat devices” to cheat federal emissions standards isn’t just relegated to four-wheeled vehicles made by Volkswagen. Harley-Davidson today agreed to settle charges it violated the Clean Air Act by paying $15 million, as well as buying back and destroying nearly 340,000 “super tuners” that emit higher amounts of certain air pollutants than what the company certified to EPA.

The Environmental Protection Agency and the U.S. Department of Justice announced the settlement [PDF] on Thursday, resolving a complaint accusing Harley-Davidson, Inc. of manufacturing and selling approximately 339,392 motorcycle tuners.

According to the complaint [PDF], since at least 2008, Harley-Davidson has manufactured and sold two types of aftermarket defeat devices, known as “super tuners,” that alter the emissions controls of some cycles.

Such devices are prohibited under the Clean Air Act for use on vehicles that have been certified to meet EPA emissions standards.

The tuners were made to allow owners to change how the motorcycle’s engine functions. By modifying the settings, tuners increase power and performance, but also increase the motorcycles’ emissions of hydrocarbons and nitrogen oxides.

The 339,392 tuners were shipped and sold at Harley-Davidson dealerships across the country.

Additionally, the EPA and DOJ say Harley-Davidson made and sold more than 12,682 motorcycles from 2006 to 2008 that were not covered by an EPA certification that ensures a vehicle meets federal clean air standards.

Under the Clean Air Act, motor vehicle manufacturers are required to certify that their vehicles will meet applicable federal emissions standards to control air pollution, and every motor vehicle sold in the U.S. must be covered by an EPA-issued certificate of conformity.

The Act also prohibits the making and sale of devices — such as super tuners or defeat devices — that bypass, defeat, or render inoperative a motor vehicle’s EPA-certified emissions control system.

To resolve the complaint, Harley-Davidson must stop selling the defeat devices in the United States by Aug. 23. The motorcycle maker will buy back all tuners in stock at dealerships across the country and destroy them.

Additionally, the company must obtain a certification from the California Air Resources Board (CARB) for any tuners it sells in the United States in the future. This certification will show that the tuners used in Harley-Davidson motorcycles do not exceed the EPA-certified emissions limits.

Harley-Davidson will also conduct tests on motorcycles that have been tuned with the CARB-certified tuners and provide the results to EPA to ensure that its motorcycles remain in compliance with EPA emissions requirements.

As part of the settlement, the company will pay a $12 million civil penalty and spend $3 million to mitigate air pollution through a project to replace conventional woodstoves with cleaner-burning stoves in local communities.

A spokesperson for Harley-Davidson said in a statement that the company does not agree with EPA’s characterization of the situation and their interpretation of the law.

“This settlement is not an admission of liability, but instead represents a good faith compromise with the EPA on areas of law we interpret differently, particularly EPA’s assertion that it is illegal for anyone to modify a certified vehicle even if it will be used solely for off-road/closed-course competition,” Ed Moreland, Harley-Davidson’s Government Affairs Director, said in a statement. “For more than two decades, we have sold this product under an accepted regulatory approach that permitted the sale of competition-only parts. In our view, it is and was legal to use in race conditions in the U.S.”

Editor's Note: This article originally appeared on Consumerist.