The US automotive safety regulator said Friday it is investigating complaints of brake failures on Harley-Davidson motorcycles that have resulted in reports of three crashes and two injuries.

"Riders report sudden brake system failure occurring without warning," said the National Highway Traffic Safety Administration, which has received 43 complaints.

About 430,000 motorcycles are involved in the probe, the NHTSA said.

Riders complained that the front brake hand lever or the rear brake foot pedal suddenly would not work. One complaint alleged that both brakes failed at the same time, resulting in a low-speed crash into a garage door.

The Harley choppers are equipped with an anti-lock braking system (ABS) aimed at boosting driver's control during sudden braking.

The NHTSA said in a statement that owners are "either unaware of or ignore" Harley-Davidson's directive to change the brake fluid every two years.

The old fluid becomes contaminated by moisture and allegedly corrodes the ABS actuator valves, resulting in the brakes failure to respond.

"While it may be true that the complainants failed to adhere to Harley-Davidson's two-year brake fluid service interval requirement, the consequent sudden and complete loss of brake(s), without warning, is a concern," the agency said.

Contacted by AFP, Harley-Davidson said: "We're aware of and cooperating with NHTSA in its investigation."