How to Bleed Brakes with Anti-Lock Braking Systems (ABS)

Does the ABS module have to be activated at the dealer for proper bleeding of the system?

How to bleed motorcycles with ABS
Most bikes with ABS are designed to allow complete flushing of the brake fluid through the ABS actuator.©Motorcyclist

Question: Thanks, MC's Ari Henning, for your how-to article on bleeding brakes in the November issue. I'm happy to see I've been doing it (mostly) right all this time. But I have a question: What do you do about bleeding brakes with an ABS system? I have a 2015 Harley Ultra Classic with ABS, and I've been led to believe it needs to be connected to a computer in order to open up the valves in the ABS pump. Is there fluid in the ABS module that can't get out unless the module is "activated" somehow? I'd hate to have to go to the dealer for what is a straightforward job on a non-ABS bike. Is this my only option aside from buying the expensive computer myself? Chris Hinds / Columbus, OH

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Answer: Most bikes with ABS are designed to allow complete flushing of the brake fluid through the ABS actuator. This is the case with Honda's ABS, as well as with several other Japanese makes. Motorcyclist's shop guy was, in a former life, an Aprilia and Moto Guzzi tech, and he says the Italian manufacturers don't bother purging the ABS module during a brake bleed. In other words, you bleed the system as though it didn't have ABS.

As with other things, however, Harley-Davidson goes its own way here and recommends using a dealer-only computer called the Digital Technician II. On a Rushmore bike like yours, the front and rear brakes are linked, and the linking is a function of the ABS. The ABS function is controlled by an electro-hydraulic control unit (EHCU), which contains brake fluid and electronically controlled solenoid valves. To properly flush the brake fluid, the EHCU must be activated by the Digital Tech or the old fluid will remain trapped in the system.

You could probably bleed your Harley's brakes as you would a non-ABS system and get away with it. But there's also your safety to think about and your bike's warranty. Paying a dealer to bleed your brakes the Harley way seems worth the expense.