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P.J., Technician
Category: Motorcycle
Satisfied Customers: 750
Experience:  10 years as a mechanic and fabricator in a privately owned, local, custom bike shop.
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I have a 2004 Harley 1200 Sportster. I replaced the rear

Customer Question

I have a 2004 Harley 1200 Sportster. I replaced the rear tire and when putting it back on I had to pry the pads a little bit and get the piston to go in to give me a little more room. Now my rear brake will not function. The piston comes out but goes back in when the pedal is released. I tried bleeding the lines but after I push out fluid, then close the bleeder and let up on the pedal, then open the bleeder it just sucks the fluid back in. Any ideas?
Submitted: 2 years ago.
Category: Motorcycle
Expert:  P.J. replied 2 years ago.

It sounds like debris has built up in your master cylinder reservoir blocking the small fluid passages located in the bottom.

This causes the piston to pull fluid back toward it from the line rather than allowing the fluid from the reservoir to make its way down into the master cylinder bore.

It is common for this to happen when a brake system is disturbed after it has been in operation for a long time. Corrosion naturally builds up on the cast aluminum and inside the steel lines. It typically can be seen as metallic streaks in the fluid. Sometimes it can be fixed easily by just flushing the reservoir and sometimes is takes a full system flush and master cylinder rebuild. It can be tough at times.

At the very least I'd say you will need to remove and disassemble the master cylinder to inspect the bore and seals and clean those passages.

I hope this helps. Thanks, P.J.

Customer: replied 2 years ago.
You have given me a starting point. Thank you for the information.
Expert:  P.J. replied 2 years ago.

You're welcome! Take care. P.J.