Front brake master cylinder - no fluid coming out

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8/16/2018 3:02 AM

I am trying to fix the front brake on my sons sx65. At first the brake was very mushy...only providing little braking power just at the end of the stroke..but it was OK because he is just learning to ride and did not need over sensitive brakes.

After a small crash the lever was totally mushy and the bike had no brakes. First I tried to bleed the lines using the bolt at the caliper but only a small amount of oil came out while lever was still totally dead feeling. I then removed the brake line at the master cylinder and there is no fluid coming out of it. If I put my finger over the hole I feel a small pressure but no fluid. I do see air bubbles coming up from first hole in the cylinder...

I am not much of a mechanic but oil should come out? Yes?

Do you think that I should rebuild the master cylinder? It seems that brake liquid was never changed (bike is 2006 model) and there was a lot of water/rust?? in the cylinder..so there is probably also dirt in the piston below the cylinder...

Suggestions?

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8/16/2018 3:10 AM

I would at least rebuild the master. Brake fluid should be changed every 2 years at the most because it absorbs water and gets contaminated. This is true on anything with hydraulic brakes. My personal rule of thumb is changing it before every riding season so its fresh.

If this were my bike, id probably rebuild the master and caliper and maybe put on a new line depending on the condition. You have to realize over time dirt and brake debris get into the caliper and fluid and travels up to the master cylinder. Makes a mess of things if its all original from 2006.

What will make bleeding easy is one of those vacuum pumps. I have one from harbor freight and it works way too good for motorcycle brakes and theres no mess on the floor.

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8/16/2018 3:59 AM

Did you try to backwards bleed it? I would start there.

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8/16/2018 5:41 AM

More than likely the cylinder is now pitted and a rebuild may not work. You may want to consider just replacing it.

Paw Paw

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